HK1038205A - Method for producing a thermoplastic coating and articles contructed therefrom - Google Patents

Description

Method for producing thermoplastic coatings and articles obtained by said method

Technical Field

The present invention relates to a non-contact coating method for producing a substantially continuous coating and articles made therefrom. The present invention also relates to a non-contact slot coating process for making various coatings and layered articles. The invention relates in particular to a method for coating a substrate comprising films, foils and papers with a hot-melt thermoplastic composition, which reduces streaking caused by particles and enables the lamination of films, films and foils and films to papers or sheets with inert hot-melt adhesives.

Background

Conventional slot nozzle coating of hot melt thermoplastic compositions onto a substrate is typically accomplished by maintaining the slot nozzle in contact with the substrate so that the nozzle is positioned on the substrate during coating. As long as the coating is not completely closed, i.e. is not porous, it is not a problem to apply the hot melt adhesive at low coating weights. In this specification, "continuous" may be used to denote a completely closed, i.e. non-porous, film or coating. However, if a completely closed, i.e. non-porous, coating is to be established, this can only be done with conventional coating methods if the amount of hot melt applied is very large.

Such large coating weights are costly. In addition, direct coating using slot nozzles can create considerable mechanical and thermal stress on the coated substrate, particularly due to the heating of the slot nozzles during coating. Therefore, coating very sensitive substrates, such as plastic films, in the conventional manner, usually with hot melts from slot nozzles, entails damage to the substrate. In addition, the large coating weight in this prior art technique results in an increase in the hardness of the coated substrate.

WO96/25902, published 29.8.1996, from h.b. fuller, MN, discloses a coating process in which heat is applied to render certain thermoplastic compositions fluid and releasable from a coating apparatus as a continuous coating without contacting the coating apparatus with the substrate to be coated.

The present invention is particularly suited to a novel coating process for a variety of other applications, including coatings on non-porous materials and coatings on porous materials. One such application is a coating on a non-porous material such as a film. The thermoplastic component typically comprises unmelted particles present as a mixture of impurities and carbon or as particulate raw materials such as fillers and additives. When these particles are of significant size and/or the slot nozzle has a small gap, the particles can collect on the coating apparatus, thereby interfering with the adhesion of the coating. The particles will block the passage of the thermoplastic material, resulting in the formation of corresponding streaks or streaks in the coated substrate. This problem is particularly prevalent in the formation of very thin films, particularly when optical quality is an important issue, such as for high quality image printing technology applications, especially where the film must be coated. Thus, the industry would find benefit in coating processes that overcome the above problems.

It is therefore a main object of the present invention to provide a novel coating process which is particularly suitable for the coating of films, foils, papers and other such materials, which process avoids the occurrence of quality irregularities and streaks, particularly when the coating is carried out at very low coating weights.

Another principal object of the present invention is to provide a coating method that utilizes a film, coated metal sheet, heat sensitive material and other sensitive material substrates that allows lamination and coating to be done "inline" or "offline" with a reduced risk of getting scrap or defective products.

It is an object of the present invention to enable the manufacture of layered articles of film-film, film-foil without the need for a reactive binder.

It is another object of the present invention to provide an improved coating process due to the application of thermoplastic compositions, particularly hot melt adhesives, to a substrate, such as a textile.

These and other objects and advantages of the present invention will be more clearly understood through the following description.

Summary of the invention

The present invention relates to a method of coating a substrate by a non-contact coating method using a thermoplastic composition and articles made therefrom. The method produces a substantially continuous coating. The present method is useful for a variety of adhesives and coating operations, and is particularly useful for those utilizing conventional slot coating techniques, heat sensitive substrates, requiring low coating weights, and/or utilizing thermoplastic compositions that include particles.

In one aspect, the invention provides a coating method in which a hot melt adhesive that has been rendered flowable by heating, such as a hot melt adhesive, is released from a coating apparatus onto a nonporous substrate as a substantially continuous coating without contacting the coating apparatus and the substrate, and then disposed on a surface of the substrate.

In another aspect, the present invention provides a coating method in which a hot-melt adhesive that has been made flowable by heating, such as a hot-melt adhesive, is released from a coating device onto a substrate as a substantially continuous coating without the coating device and the substrate coming into contact, and is subsequently coated on the surface of the substrate, wherein the distance between the coating device and the substrate is greater than 20 mm.

In another aspect, the present invention provides a coating method in which, without the film being in contact with a substrate, a hot melt adhesive, such as a hot melt adhesive, and subsequently coating the film onto a substrate by a release coating roll or by a coating method, the roll pressing the adhesive and the substrate being in direct contact with the adhesive film, or a release coated second substrate disposed on a surface of the thermoplastic composition not in contact with the first substrate, wherein a thermoplastic composition that has been rendered flowable by heating, such as a hot melt adhesive, is applied as a substantially continuous coating without contact between the coating device and the roller, i.e. a surface onto which a non-porous film is released from, for example, a coating device onto a substrate and subsequently disposed on a substrate.

In another aspect, a coating method wherein a thermoplastic composition that has been rendered flowable by heating, such as a hot melt adhesive, is released from a coating device onto a substantially nonporous substrate as a substantially continuous coating without contacting the coating device with the first substrate, and then disposed on the surface, wherein the coating is then reheated and then contacted with a second substrate.

The invention also relates to a method for laminating, in addition to film-film, film-foil laminates, in particular for laminating, for example, transparent film materials to a substrate, in particular a substrate of printed paper or cardboard, which avoids the above-mentioned disadvantages of the prior art and enables such film-film, film-foil laminates to be produced using inert hot-melt adhesives.

For heat-sensitive substrates, it is desirable to coat the thermoplastic composition at a temperature of less than about 160 deg.C, more desirably less than about 125 deg.C, and even more desirably less than about 110 deg.C to reduce thermally-induced stresses on the coated substrate. Alternatively, the distance between the coating device and the coated substrate may be increased to allow sufficient cooling of the molten thermoplastic composition prior to contacting the heat sensitive substrate. This is particularly advantageous for coating and adhering heat-sensitive substrates to one another.

The thermoplastic composition preferably exhibits rheological properties such that the complex viscosity at high shear (1,000 radians/second) is less than about 500 poise and the complex viscosity at low shear (1 radians/second) is less than about 1,000 poise. Pure thermoplastic resins can be used in the process of the present invention as long as the viscosity of some of the unmixed materials is very low. However, compounding hot melt adhesives is desirable because of the ability to independently control viscosity characteristics, time intervals, etc. The composite hot melt adhesive is also advantageous to ensure adequate adhesion on the carrier substrate or delayed debonding characteristics of the coating after bonding to the substrate.

The composite coatings produced by the described methods can be used in a variety of applications that require a substantially continuous coating of consistent, hole-free type. To reduce cost and improve tactile quality of the coated substrate, the coating should be less than 50-60 grams/meter²And particularly desirably less than 30 g/m². Coating weights of less than 10 g/m 2 are achievable in many cases.

The synthetic coating is preferably used for the manufacture of laminates of paper or board, in particular printing paper. The coating method of the present invention is particularly advantageous for production, since the manufacturing steps are less than those of the prior art coating methods. Increasing the throughput and reducing the amount of coating per unit area results in lower costs for the coating and corresponding articles than in the prior art.

However, the coating method should not be limited to applications using a non-porous substrate. The coatings of the present invention can also be used with apertured substrates. Various aspects of the invention may be utilized herein, including methods of releasing a thermoplastic composition from a coating apparatus onto a nonporous substrate at a distance greater than 20mm between the coating apparatus and the substrate, and methods of pressing a hot melt adhesive against a porous substrate by a release coating roller in direct contact with an adhesive film.

Articles described herein include articles having at least one first layer that is a non-porous substrate and at least one second layer that is a coating or adhesive layer made by the coating methods described above.

Brief description of the drawings

Fig. 1-10 illustrate preferred embodiments of the method of the present invention wherein a substantially continuous thermoplastic coating is formed and adhered to a substrate.

More particularly, FIG. 1A depicts the basic structure of a coating and laminating apparatus for controlling the method of the present invention;

FIGS. 1B and 1C depict a similar basic structure as the device;

FIGS. 2-4 depict the lamination of the present invention at various locations of the coating apparatus;

fig. 5A and 5B are diagrams illustrating a lamination and transfer coating method of the present invention.

Fig. 6-10 depict layered articles of the present invention that include adhesive activated layered articles.

Detailed description of the invention

In the method of the present invention, a preferably substantially air-free molten thermoplastic composition, such as a hot melt adhesive, is initially provided in the form of a substantially continuous, non-porous film which is only subsequently contacted with a substrate, a conveyor roll or some other support. Typically, the composition is discharged from a coating or release device in such a manner as to exit the device as a substantially continuous film. Since the coating apparatus has been used for a coating operation in which the coating apparatus is directly contacted with a substrate, a common coating apparatus is a slot nozzle. Therefore, the known hot-melt coating device can be used in the method of the invention, in which the slot nozzle is separated from the substrate and adjusted to have a suitable spacing from the substrate.

When the flowable hot melt adhesive or thermoplastic composition exits the coating apparatus, it does not contact the substrate, but moves a distance when the continuous film is suspended between the coating apparatus and the substrate. The coating device may initially be in contact with the substrate to secure or adhere the thermoplastic composition to the substrate, which ensures that thermal or mechanical damage to the substrate from contact with the coating device is not caused. On the other hand, the thermoplastic composition is discharged as a substantially continuous film through the nozzle and does not descend until contacting the substrate. The advancing generally continuous film leader of thermoplastic composition is bonded or otherwise secured to the substrate by contact with the substrate. In the case of heat sensitive materials, it is desirable to advance the substrate through a drive roller before the thermoplastic composition contacts the substrate to avoid the formation of agglomerates of molten material that will melt through the substrate.

FIGS. 1A,1B and 1C schematically depict a mechanical device suitable for controlling the method of the present invention. Fig. 1A and 1B depict an embodiment in which the thermoplastic composition is release coated from a coating device 3 onto a first substrate 1 and subsequently a second substrate 4 is spread over the free surface of the coated adhesive by means of a press roll 5. It will be appreciated that modifications may be made to the structure in other embodiments and particularly where the use of a second base layer 4 is not necessary under all conditions. Subsequently, the thermoplastic composition is pressed directly onto the first substrate by means of a press roll 5. For such embodiments, the press roll 5 may be release coated, for example, using a steel roll with a polytetrafluoroethylene surface layer.

As shown particularly in fig. 1A and 1B, the substrate 1 is secured in proper mating position by a series of idler rollers (idler rollers) 2 prior to approaching the coating apparatus 3. The substrate 2(4) is randomly adhered to the coated surface by a press roller 5. The substrate 1 is defined as the first substrate which is in contact with the substantially continuous thermoplastic film. The base layer 1 is any base layer that is generally provided in rolls of, for example, nonwoven, paper including release coated paper and various films, sheet metal, and other materials. The embodiment of fig. 1A is particularly suitable for coating porous substrates, in which case the contact point of the pressure roller 5 with the adhesive film and the first substrate is relatively far away. Fig. 1B is particularly useful when the substrate 1 is non-porous, which means that air does not readily pass through the substrate. In the case of a thin metal sheet laminate, the substrate 1 is usually a film. The base layer 2 may also be provided in a roll and be of the same or different material as the base layer 1. However, the substrate 2 may also be a special material such as a super absorbent polymer, or a release-coated web material that can be pulled out of the adhesive coating.

Fig. 1C depicts an embodiment in which the adhesive film is first pressed onto the first substrate 1 by a press roll 5, which press roll 5 is part of a press station shown later by rolls a and B in fig. 2-10.

Subsequently, the second base layer 4 is disposed on the free surface not in contact with the first base layer 1 at a laminating station (station) formed by the rollers C and D.

Fig. 2-10 depict various preferred embodiments of the present invention wherein a thermoplastic composition, such as a hot melt adhesive, is applied to a first substrate and subsequently laminated to a second substrate. In each description, the base layer 2 is arbitrary, wherein the present invention in its broadest aspect employs only a single continuous non-porous film, which is formed by a non-contact coating method and is coated onto a single base layer. In the absence of a second substrate, fig. 5B depicts a transfer coating operation as the molten composition is first applied to a release coating roll that is thereafter contacted with the first substrate at a press.

In the absence of the secondary substrate, in embodiments where the thermoplastic coating or hot melt adhesive is in contact with the primary substrate, or when the secondary substrate is porous, it is important to provide a release coating, such as silicon, teflon or release paper, on the roll associated with the adhesive or porous substrate to prevent adhesion of the thermoplastic composition to the roll, as shown in fig. 6 and 7. The pressure roller forces air from between the thermoplastic coating film and the substrate to ensure that no air is trapped between the first substrate and the thermoplastic composition. The roller a may be a steel cylinder which contributes to heat conduction, while the roller B, which is generally a press roller, is made of a rubber material. In some cases it may be more desirable to use rubber for roll a and steel cylinder with an outer release coating for roll B.

Fig. 3-10 illustrate that the nozzle position can be changed from a perpendicular position to a parallel position relative to the substrate position.

Fig. 8 and 9 depict a second substrate laminated to the first substrate at a location remote from the coating apparatus. In this embodiment, the roller C is preferably heated to restore or extend the time between hot melt adhesive or thermoplastic coating before being laminated to the second substrate. The temperature of roll C was varied between about 30-100℃ to allow lamination between rolls C and D. Alternatively, roll C may employ a chill roll to promote the rate of solidification of the thermoplastic coating or hot melt adhesive. Which is useful where a layered article is manufactured for intermediate storage. The base layer laminated at the roll pressing may be in a net form or in a thin layer shape. Where roll C is a chill roll, as shown in fig. 10, the method of the present invention can be used to make a substrate, such as a film coated on one side with a thermoplastic composition that can be used, for example, in a heat sealing operation. Where desired, another layer of release paper may of course be added, as shown in FIG. 9, to protect, for example, the heat seal material for intermediate storage.

The distance between the coating means and the substrate (or the release coating roll in the case of transfer coating in the absence of a second substrate in fig. 5B) is at least 0.5mm, preferably at least 2 mm. The maximum distance between the application device and the substrate is only limited by the actual circumstances, in particular when the application device is brought into a vertical position. Depending on the nature of the thermoplastic composition coating, the spacing should be less than about 5m, more preferably less than about 3m, still more preferably less than about 1m, particularly preferably less than about 500mm, and most preferably less than about 2-20 mm. A particular advantage is that during coating by airborne contaminants and air currents, the area between the coating apparatus and the substrate is isolated to prevent deformation of the coating prior to contact with the substrate. This is particularly the case when the distance between the coating means and the substrate is greater than about 500 mm.

The spacing is highly dependent on the viscosity of the thermoplastic composition being coated and the time between applications. In the case of a protective film manufactured in this manner, it is assumed that the thermoplastic composition is sufficiently cooled in its suspended state so that any filaments or fibers having a viscosity and cohesive force that appear on the surface of the base layer cannot enter the coating layer, and further the thermoplastic composition is sufficiently melted to sufficiently adhere to the base layer. The greater the distance between the coating device and the press roll, the cooler the hot melt adhesive or coating will be before it contacts the first substrate. For some adhesive compositions, this cooling can adversely affect the adhesion (or setting) on the substrate. Thus, the substrate may be passed through a heated roller before being pressed, or a heated roller may be used if the spacing between the roller and the coating device causes the coating or adhesive to cool to such an extent that it no longer sufficiently adheres or secures to the substrate.

The coating may contact the substrate at any angle (compare, e.g., fig. 3 and 4). However, it has been found that for certain applications, such as protective films, it is highly advantageous for the coating later to contact the substrate in a generally horizontal orientation as shown in FIGS. 1A,1B,2,6 and 8. To accomplish this, a roller may be disposed along the movement path of the substrate as it passes through the coating apparatus so that the substrate has a generally vertically upward direction. Thus, coating devices such as slot nozzles are disposed largely horizontally beside the roll so that the coating can move from the side to the substrate surface.

The diameter of the applicator roll is preferably from about 15mm to about 50mm and the radial nozzle is slightly above the center of the applicator roll so that the angle at which the thermoplastic coating contacts the substrate is slightly less than 60 when the substrate is farther from the nozzle. The coating head is adjusted by one of ordinary skill in the art to optimize uniform flow and distribution of the thermoplastic coating across the entire operating width.

Thereafter, the sufficiently cooled coating contacts the surface of the substrate and adheres to the surface without penetrating deeply into the substrate. If the thermoplastic coating is a composition that has a significantly reduced viscosity after sufficient cooling, the resulting coated substrate laminate can be rolled and stored. On the other hand, this work can be achieved by providing a release coating secondary substrate, such as Silicone-coated paper, on the surface of the bond coat. The layered article may then be used at some later time. The laminate is attached by any suitable attachment technique, including ultrasonic welding, heat sealing or more commonly adhesive adhesives.

Before any further work, it is preferred to make the coating in "inline" form immediately. An example of an inline process to which the invention is particularly suitable is disclosed in DE 19546272C 1 of Billl * ferMaschinenfabrik GmbH, to which reference is made for the present invention. The coated surfaces facing away from the substrate may be so tacky that they can be used as a structural adhesive or for lamination of other substrates, and thus it can also be used to bond the coated substrate to another substrate. Other substrates that may be simultaneously bonded or laminated in this manner include: sound absorbing materials, superabsorbent polymers, elastic strands and webs, fabrics, films, foils, paper, cardboard, metal, and various permeable cover materials such as nonwovens or apertured films. These materials may be in roll, sheet or pellet form.

In a preferred embodiment, the substrate to be laminated is paper or cardboard, especially printed paper, treated photographic paper or printed cardboard, for example for book covers, graphic postcards, calendars, posters, high-quality packaging materials, gift packages and the like. The laminate material may be a synthetic film material, paper, textile material or any other flexible material suitable for lamination. However, the laminate is preferably a synthetic film material commonly used for such lamination, particularly a clear transparent film material.

These film materials typically comprise flat or printed films made at a minimum generally from oriented polypropylene, polyethylene, polyesters such as Mylar , polyacetates, nylon, acetate fibers, etc. having a thickness of from about 5 microns to about 50 microns. These films are typically laminated or sealed to printed paper or board stock. Synthetic materials are commonly used for film-film, film-thin metal sheet, and metal-coated substrates are commonly used for layered articles. These types of layered articles are commonly used in industries such as graphic printing techniques and packaging. With the method of the invention, such a laminate can be manufactured using an inert hot melt adhesive instead of the commonly used reactive adhesive.

Typically, the outlet temperature of the thermoplastic composition is less than about 240 ℃ and thus well below the standard polymer extrusion temperature of 300 ℃. Although the temperature of the thermoplastic composition exiting the coating apparatus may be from about 80 c to about 180 c or greater, the non-contact coating system of the present invention allows coating to be accomplished at very low temperatures. For this embodiment, it is desirable to effect coating at a temperature of less than about 160 deg.C, more desirably less than about 140 deg.C, and particularly desirably less than about 120 deg.C and less than about 110 deg.C. As previously mentioned, heat sensitive materials can also be applied in a manner that allows sufficient cooling by increasing the distance between the coating device and the substrate being coated at the same time with higher coating temperatures. Thus, materials that are typically mechanically and/or thermally very sensitive to conventional coating methods (e.g., very small thickness films) can be coated using the methods of the present invention. Such sensitive materials include small gauge polyethylene materials, small fabric unit mass nonwovens and the like.

A significant advantage of the present invention is that a substantially continuous coating can be produced at very low coating weights. Even with conventional commercial hot melts, can be used at about 0.5 g/m²To 50-60 g/m²Desirably not more than about 30 g/m²More desirably not more thanAbout 20 g/m²The coating amount of (A) is particularly preferably 10 g/m 2 to 20 g/m²Coating amount of less than 10 g/m²To produce a continuous layer. But greater than 60 g/m²The coating weight of (a) can be used for other operations where reducing mechanical and thermally induced stresses is a primary problem.

The very thin coating produced according to the invention not only contributes to the economic advantage of the process according to the invention, but also achieves a very low stiffness of the material, so that it is very close in properties to the uncoated substrate.

Thermoplastic composition

The thermoplastic materials mentioned above may be used in the present invention, as may thermoplastic polymers including polyethylene, polypropylene, copolymers of olefins, particularly ethylene and (meth-) acrylic acid; copolymers of olefins, in particular ethylene, and (meth-) acrylic acid derivatives, in particular (meth-) acrylates; copolymers of olefins, particularly ethylene, and ethylene compositions, particularly ethylene carboxylates such as vinyl acetate; thermoplastic rubbers (or synthetic rubbers) such as styrene-isoprene, styrene-butadiene-styrene, styrene-ethylene/butylene-styrene, styrene-ethylene/propylene-styrene block copolymers available under the trade names Kraton , Solprane  and Stereon ; metallocene-catalyzed polymers, in particular polymers obtained from ethylene and/or propylene; polyolefins, such as ethylene, polypropylene and amorphous polypropylene (atactic polyalphaolefins), such as Vestoplatst  703 (Huls); a polyester; a polyamide; ionomers and corresponding copolymers; and mixtures thereof. Such a thermoplastic material is also used in the coating process of the invention in the non-mixed state, thereby ensuring a very low viscosity of the thermoplastic material. However, it is desirable to have a hot melt adhesive that independently satisfies tack characteristics, time between tack, and various other characteristics. Hot melt adhesives typically have a melt flow index required for processing at very low temperatures. A common hot melt is a fluid sufficient to operate at a temperature of about 60 c to 175 c. Thus, a variety of known hot melt wet compositions can be used in the present invention.

Materials which are impermeable to liquid water but permeable to water vapour, so that the coating can be "breathable", can also be produced using suitable hotmelts, such as the hotmelt disclosed in DE-a-4121716.

In addition to the commonly known hot melt adhesives, the inclusion of a water-soluble, salt-containing (body fluid) insoluble polymer, such as the Eastman AQ copolyester available from Eastman, is also particularly suitable for use in protective films that are impervious to body fluids but readily soluble in water. This feature is very important for the manufacture of flushable and synthetically dispensable health products. In addition, there are applications requiring water permeability. Thus, this coating method is also suitable for coating water-soluble and/or biodegradable thermoplastic materials.

For lamination adhesives for transparent substrates, thermoplastic polymers comprising substantially or entirely one or more ethylene/methyl acrylate copolymers (EMA 'S) and/or ethylene/n-butylmethacrylic acid copolymers (EnBA' S) are desirable. EnBA copolymers are currently the most desirable polymers.

More desirably, the thermoplastic composition exhibits a rheology such that it can be applied at a level of less than about 50-60 g/m²And preferably less than about 30 g/m²The amount of coating produces a substantially continuous coating. Generally, the rheological properties are preferably within the rheological window region where the complex viscosity is less than about 500 poise at high shear (1,000 rad/sec) coating temperatures and less than about 1,000 poise at low shear (< 1 rad/sec) coating temperatures. On the other hand, the preferred thermoplastic compositions exhibit newtonian regions at low shear rates and shear thinning at higher shear rates. Thermoplastic compositions having a wide window of application are compositions which exhibit rheological properties under various operating conditions, in particular at relatively low application temperatures. Narrower application windows are those which only meet the rheological parameters under very specific conditions,

the applicant estimates that complex viscosity and high shear are related to the operating conditions at the slot die exit. Compositions with too high a complex viscosity at 1,000 rad/sec require very high pump pressures to exit the coating apparatus. A film with a coarse tuning gap of greater than 3mm can be used to process these materials but can result in higher coating weights.

During suspension over the substrate, complex viscosity and low shear are related to the deposition of the coating on the substrate. If the low shear is too high, the coating may not adhere sufficiently to the substrate and/or the thermoplastic composition may produce a striped, discontinuous coating at the nozzle. If the low shear viscosity is too low, the coating may penetrate into the base layer, thereby forming poor barrier properties.

The unmeasured elongation properties also greatly affect the melt strength. The addition of higher levels of branching and low density polymeric materials can greatly affect melt strength. More desirably, the composition meets the target rheological parameters at low application temperatures of less than about 177 ℃, desirably less than about 160 ℃, more desirably less than 140 ℃, more desirably less than about 125 ℃, and most desirably less than about 110 ℃.

Thus, many known hot melt adhesive compositions are well suited for use in the coating process of the present invention. Hot melt adhesives typically include at least one thermoplastic polymer, at least one plasticizer, and at least one tackifying resin. Such suitable hot melts include up to 50% by weight of thermoplastic polymer, up to 40% by weight of plasticizer and up to 70% by weight of tackifying resin. For hot melt adhesives that are not pressure sensitive, waxes are typically used at concentrations up to about 30% by weight of the adhesive.

In general, the hot melts of the invention additionally comprise one or more tackifying resins, plasticizers or oils, and waxes in addition to conventional additives and adjuvants, such as stabilizers, antioxidants, pigments, UV stabilizers or absorbers, fillers, etc. Plasticizers and tackifying resins for hot melt adhesives are known.

Oils such as naphthenic petroleum oils are desirable plasticizers. As tackifying resins per se, the resins generally known for this purpose, in particular aliphatic, cycloaliphatic and/or aromatic hydrocarbon resins, ester resins and other corresponding resins, are suitable. It is currently preferred to use aliphatic or aromatic modified hydrocarbon resins. Desirable aliphatic resins are aliphatic hydrocarbon resins such as Escorez  5000 series available from Exxon chemical company, Housou, TX, Arkon  P and M series available from Arakawa Chemal, Inc., and Regalite  available from Hercules corporation, Wilmington, DE. Both rosin and rosin ester resins can be used in the present invention. One such hydrogenated rosin acid tackifying resin is Foral  AX available from Hercules. Modified hydrocarbon resins such as modified terpenes including the Zonatec  series available from Arizona chemical corporation of Panama, FL, the alpha-methylstyrene resin of the Kristalex  series available from Hercules, Inc., and the styrene terpene hydrocarbons of the Uratack  series available from Arizona chemical corporation may also be used in the present invention. These components are mixed in a known manner to produce the hot melts which can be used in the present invention.

Waxes are also useful in the present invention. These waxes include synthetic high melting point waxes such as Paraffin  available from Sasol (south Africa) or Fischer Tropsch wax available from Shell Malaysia under the trademark Petrolite, and high density low molecular weight polyethylene waxes available from Marcus chemical under the trademark Marcus . AC8 is another effective polyethylene wax obtained from Allied chemical. Microcrystalline paraffins and paraffin waxes may also be used in the present invention.

The laminating adhesive preferably comprises up to 100% of at least one thermoplastic polymer as described above; 0-50% of an aliphatic hydrocarbon resin; 0-20% of aromatic hydrocarbon resin; 0-40% rosin and 0-20% paraffin wax, the components and amounts thereof being selected so that the adhesive is applied in-line to the laminate and/or laminate substrate and the laminate is subsequently laminated in-line to the substrate.

More desirably, for a thin film stack, the binder comprises the following components: up to 100% of at least one EMA and/or EnBA copolymer; 0-50% of hydrogenated aliphatic hydrogen resin; 0-20% of an alpha-methylstyrene resin; 0-40% of hydrogenated rosin and 0-20% of polyethylene paraffin.

The hot melt adhesive used to carry out the process of the invention comprises in the simplest case, in principle or even entirely, one or more stages of EMA and/or EnBA copolymer. EMA and EnBA copolymers are available from ElfAtochem under the trademark Lotryl  and from Quantum Chemal and Exxon Chemal under the trademark Optema . A variety of different stages of EMA and EnBA copolymers are suitable, differing primarily in ester content, Melt Flow Index (MFI) and melting point.

In the presently preferred embodiment, the hot melt adhesive comprises substantially 35-60% EnBA or EMA; 30-50% hydrogenated aliphatic hydrogen resin or about 10% aliphatic hydrogen resin; 0-30% of hydrogenated rosin and 0-10% of polyethylene paraffin, and a small amount of stabilizer. In certain preferred embodiments, the thermoplastic polymer of the hot melt adhesive is a single stage EnBA copolymer, typically at the small end of the MFI range (i.e., MFI less than 10 g/10 min). In other preferred embodiments, the thermoplastic polymer comprises more than one stage of EnBA, and in some cases, at least two of the two or three different stages preferably have MFIs that differ by a factor of at least 4-10 (i.e., one stage has an MFI that is 4 times greater than the other stage).

The hot melt of the present invention can be used at very low operating (or working) temperatures to prevent deformation of the thermo-sensitive plastic film, while exhibiting excellent flow characteristics at such low temperatures. For example, the hot melts of the present invention can be coated and laminated onto a laminate. For the thermo-chromatic film, non-contact coating is very advantageous, so that excellent film formability is achieved and a layered product may exhibit high glossiness.

The laminating adhesives of the present invention will result in higher hot melt coating clarity to achieve higher gloss without impairing the clarity and color reproducibility of the print on the substrate.

For the process of the present invention, in addition to the setting properties, the hot melts of the present invention will exhibit excellent (higher) hot tack and time-between-time properties. These hot melts, as in the image printing industry, satisfy the processing conditions in straight knurling and cutting.

The layered article manufactured according to the present invention exhibits high heat resistance and high ultraviolet ray resistance characteristics and accordingly does not cause peeling or yellowing. Also, after thermoforming and knurling, no film release was observed when using the hot melt formulation of the present invention.

The following non-limiting examples further help illustrate the invention.

Examples

As shown in table 1 below, the hot melt adhesives were made from different hot melt polymers, tackifiers and plasticizers.

Examples 1 to 8

TABLE 1

Composition (I)	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Fruit of Chinese wolfberryExample 7	Example 8
									Lotryl  17 BA 07EnBA copolymer	23	40	35	10	23	-	-	-
Lotryl  35 BA 40EnBA copolymer	15	-	-	20	15	20	15	15
									Lotryl  35 BA 320EnBA copolymer	17	-	-	30	17	10	16	15
Escorane  UL 150-19EVA copolymer	-	-	-	-	-	20	24	23
									AC-8 polyethylene wax	5	10	-	-	5	-	5	-
Paraffint  C80 polyethylene wax	-	-	-	-	-	10	-	-
									Mobil wax 145 paraffin wax	-	-	-	-	-	-	-	5
Escorez  5300 hydrocarbon resin	28	38	38	38	-	23	28	30
									Foral  AX abietic acid resin	10	10	25	-	28	15	10	10
Kristalex  F85 alpha methyl styrene resin	-	-	-	-	10	-	-	-

A hot melt adhesive corresponding to the components described in examples and 1 and 7 was applied to the substrate using a modified PAK600 laminator from Krosnert Hamburg, germany, the construction of this machine was substantially similar to that shown in fig. 1B. With this machine, the adhesive film is pressed directly onto the first substrate 1 by the press roll 5 or the second substrate 4 is pressed onto the first substrate and the adhesive while still passing through the press roll 5. In the experiment, both methods were attempted. The compounding temperature of the hot melt was 140 ℃ for the composition of example 1 and 110 ℃ for the composition of example 7. As can be seen from fig. 14, these compositions exhibit suitably low viscosities. The graph illustrates the viscosities in 1 and 7 above.

The coatings were formed on Polyester films (Polyester RN 36, manufactured by Duitz Folien, Taunussein-Wehen, Germany) and high density polyethylene films (HDPE KC 3664.00, manufactured by Mildenberger and Willing, Gronau, Germany).

As second substrates (used herein), these films are also used. In other tests, silicon paper was used instead. The test can also be carried out using printed paperboard as the secondary substrate.

At a processing speed of about 70 m/min, the coating weight is 5-6 g/m²。

In different experiments, the adhesive film was released from the coating slot nozzle at different distances from the first substrate coated with adhesive. In other experimental groups, it has been found that the distance between the slot nozzle and the substrate can be varied from a few millimeters to 500mm or more without significantly affecting the coating quality by using a vertical structure (similar to fig. 3-5,7,9 and 10).

In these tests, the adhesive discharged from the coating slot nozzle was directly applied to the first substrate using a pressure roller 5 provided with a release coating. It has been found that the adhesive does not adhere to the press roll. It is not necessary to measure the nip pressure, but the nip roller should press against the substrate with a layer pressure of 7-8 bar.

It has been found that the adhesive applied to the first substrate does not allow the pressing station to leave air between the adhesive and the first substrate.

In other tests, a second substrate was laminated to the adhesive layer by a second set of rollers located in the flow path of the substrate upstream of the pressure roller 5. The laminates can also be tested for streaking, entrapped gas or other defects of use using the same films or release papers described above.

The layered article thus produced does not contain gaps. Also, no streaking, entrapped gas or other defects of adoption were observed.

In a similar manner, layered articles were made from the same type of film, with other binders than examples 2-6 in Table 1. The results were as satisfactory as using the tacky components in examples 1 and 7.

Claims (28)

1. A coating method, characterized by: a hot melt adhesive that has been rendered flowable by heating is released from a coating device as a substantially continuous coating onto a substantially nonporous substrate without contacting the coating device and the substrate, and is subsequently disposed on a surface of the substrate.

2. A coating method, characterized by: a hot melt adhesive which has been rendered flowable by heating, is released from a coating device onto a substantially non-porous substrate as a substantially continuous coating without contact between the coating device and the substrate, and is subsequently disposed on the surface of the substrate, wherein the distance between the coating device and the substrate is greater than 20 mm.

3. A coating method, characterized by: a hot melt adhesive which has been rendered flowable by heating is provided in the form of a substantially continuous non-porous film without contact of the coating device with the substrate or a roll, and is subsequently coated onto a substrate by means of a stripping roll in direct contact with the adhesive film, which roll compresses the adhesive and the substrate.

4. A coating method, characterized by: a hot melt adhesive that has been rendered flowable by heating is released from the coating device onto the release-coating roller as a substantially continuous film without contact between the coating device and the roller, and is subsequently coated onto a substrate surface.

5. A coating method, characterized by: providing a hot melt adhesive that has been rendered flowable by heating in the form of a substantially continuous non-porous film without contacting the film with a substrate, and subsequently coating the film onto a first substrate through a release substrate disposed on a surface of the hot melt adhesive, wherein the adhesive does not contact the first substrate.

6. A coating method, characterized by: in the form of a substantially continuous non-porous film, a hot melt adhesive that has been rendered flowable by heating without contacting the film with a substrate is provided, and the film is then coated onto a release substrate and then transfer coated onto a second substrate.

7. A coating method, characterized by: a hot melt adhesive that has been rendered flowable by heating as a substantially continuous coating is released from the coating device onto a first substrate and then disposed on a surface of the first substrate without the coating device and the first substrate contacting, wherein the coating is reheated and then contacted with a second substrate.

8. A coating method, characterized by: providing a hot melt adhesive that has been rendered flowable by heating in the form of a substantially continuous non-porous film without contacting the film with a substrate, and subsequently applying the film to a substantially non-porous substrate.

9. A coating method, characterized by: in the form of a substantially continuous non-porous film, a thermoplastic material that has become flowable by heat is released from a coating device at less than about 240 ℃ without the film and a substrate contacting, and the film is subsequently coated onto a substrate.

10. A coating method, characterized by: providing a thermoplastic material that has been rendered flowable by heat in the form of a substantially continuous non-porous film without contacting the film with a substrate, and subsequently applying the film to a substrate, the coating having a complex viscosity of less than about 500 poise at an application temperature and at about 1000 rad/sec.

11. A coating method, characterized by: a thermoplastic coating having a complex viscosity of less than about 500 poise that has been rendered flowable by heating at a coating temperature and at about 1000 rad/sec is released from the coating apparatus onto a nonporous substrate as a substantially continuous coating without contact between the coating apparatus and the substrate, and is subsequently coated onto the surface of the substrate.

12. A coating method, characterized by: a thermoplastic coating having a complex viscosity of less than about 500 poise at a coating temperature and about 1000 rad/sec which has been rendered flowable by heating, released from said coating apparatus onto a substrate as a substantially continuous coating without contact between the coating apparatus and the substrate, and subsequently applied to the surface of said substrate, wherein the distance between said coating apparatus and the substrate is greater than 20 mm.

13. A coating method, characterized by: a thermoplastic coating having a complex viscosity of less than about 500 poise when heated to a coating temperature and about 1000 rad/sec which has been rendered flowable, released from the coating apparatus onto a first substrate as a substantially continuous coating without contact between the coating apparatus and the substrate, and subsequently disposed on the surface of the first substrate, wherein the coating is reheated and thereafter contacted with a second substrate.

14. A coating method, characterized by: a thermoplastic coating having a complex viscosity of less than about 500 poise at a coating temperature and about 1000 rad/sec which has been rendered flowable by heating, released from the coating apparatus onto a release coating roll as a substantially continuous coating without contact between the coating apparatus and a substrate, and subsequently disposed on a surface of a substrate,

15. the method according to claims 8-14, characterized in that: the thermoplastic coating has a complex viscosity of less than about 1000 poise at a coating temperature and at about 1 rad/sec.

16. The method according to claims 1-15, characterized in that: the base layer is selected from the group consisting of films, thin metal sheets, paper, and combinations thereof.

17. The method of claim 16, wherein: the first and second substrates are selected from films, foils, papers, coated papers, composite films, and other laminates, and the binder is an inert binder or a reactive hot melt binder.

18. The method according to claim 15 or 16, characterized in that: the coated substrate includes a heat seal material.

19. The method of claims 1-18, wherein: the coating device is a slot nozzle.

20. The method of claims 1-19, wherein: the coating has less than about 60 grams/meter²Area weight of (c).

21. The method of claims 1-20, wherein: the coating has less than about 30 grams/meter²Area weight of (c).

22. The method of claims 1-21, wherein: the coating has less than about 10 grams/meter²Area weight of (c).

23. The method according to claims 8-14, characterized in that: the thermoplastic composition is released from the coating device at a temperature of less than about 160 ℃.

24. The method according to claims 8-14, characterized in that: the thermoplastic composition is released from the coating device at a temperature of less than about 110 ℃.

25. The method of claims 1-24, wherein: a first substrate is adhered to at least one of an "on-line" or "off-line" second substrate.

26. The method of claims 1-25, wherein: the distance between the coating device and the substrate is in the range of about 0.5mm to 500 mm.

27. A book cover made by the method of any one of claims 1-26.

28. A layered article made by the method of any one of claims 1-26.