JPH11208107A - Disintegrable recording sheet and method for producing the same - Google Patents

Abstract

(57) Abstract: A recording material comprising a water-soluble ink-receiving layer (recording layer) and a biodegradable base material, which is generally disintegrable and has a high linear light transmittance, particularly a recording material for OHP and the like. To provide a manufacturing method. A recording layer mainly composed of a hydrophilic polymer compound composed of a repeating unit represented by the following formula (1) or (2) is provided on a substrate made of a polylactic acid-based polymer. And a linear light transmittance of 70% or more. -[AY]-(1)-[AYAR]-(2) In the above formulas (1) and (2), A is the following formula (3): (In the above formula (3), X is a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms. In addition, x, y, and z are 0 or 1 or more positive numbers, and X is 1 or more carbon atoms. Is satisfied by the following two formulas: 44 (x + z) / (molecular weight of α-olefin oxide having 3 or more carbon atoms) y = 80/20 to 94/6.) A polyalkylene oxide residue, Y is an organic compound residue having two active hydrogens, and R is a dicarboxylic acid compound residue or a diisocyanate compound residue.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a sheet having a characteristic of disintegrating in a natural environment and having excellent transparency. In particular, the present invention relates to a collapsible recording sheet having excellent ink jet recording characteristics and a method for producing the same.

[0002]

2. Description of the Related Art A recording sheet provided with a recording layer mainly composed of a hydrophilic polymer compound is currently used as a recording material, particularly as a transparent recording material for OHP. Recently, water-soluble inks containing water or alcohol as a main component have been frequently used as recording inks from the viewpoint of safety. In addition, in the ink jet recording method in which ink droplets are made to fly and adhere to a recording material to perform recording, a water-soluble ink is often used from the viewpoint of high-speed printing suitability and multicolor printing suitability. In order to meet these demands, there has been an increase in the number of recording sheets provided with a recording layer containing a hydrophilic polymer compound as a main component in a receiving layer capable of absorbing and fixing a water-soluble ink.

[0003] By the way, many of the substrates supporting the recording layer are made of physically stable synthetic polymers such as polyethylene, polypropylene and aromatic polyester. In particular, when transparency is required, biaxially oriented polypropylene (OPP) and biaxially oriented aromatic polyester (OPE)
T) and the like. However, these plastic sheets do not collapse in the natural environment, and do not lose underground even when landfilled. This is one of the factors that hinder the extension of landfill life.

By the way, sheets made of a biodegradable polymer, which have been actively studied in recent years, are expected to solve the above problems. Above all, aliphatic polyesters have been particularly studied since they become non-toxic and safe low-molecular compounds after biodegradation. As the biodegradable aliphatic polyester, a polyester obtained by ring-opening polymerization of a cyclic lactone, a synthetic aliphatic polyester, a polyester biosynthesized in a bacterial cell, an aliphatic polyfunctional alcohol and an aliphatic polyfunctional carboxylic acid are condensed. The resulting polyester and the like can be mentioned.

More specifically, typical polyesters obtained by ring-opening polymerization of cyclic lactones include poly-ε-caprolactone, poly-δ-valerolactone, poly-β-methyl-δ-valerolactone and the like. It is listed. Examples of the synthetic aliphatic polyester include a cyclic acid anhydride and an oxirane, for example, a copolymer of succinic anhydride and ethylene oxide, propylene oxide, or the like. Examples of the polyester biosynthesized in the cells include polyhydroxybutyrate, polyhydroxybutyrate / valylate, and the like. Further, as the polyester obtained by condensing an aliphatic polyfunctional alcohol and an aliphatic polyfunctional carboxylic acid, succinic acid or adipic acid, or a dicarboxylic acid component consisting of both, and ethylene glycol or butanediol, or both of these. Representative examples thereof include aliphatic polyesters having a diol component as a main structural unit. Further, as a different polyester, a compound such as suberic acid, sebacic acid, dodecanedioic acid, or a polyester obtained by condensing anhydrides or derivatives thereof with an acid component, and hexanediol, octanediol, or cyclohexanediene with an alcohol component. Polyesters obtained by condensing compounds such as methanol and derivatives thereof, and tri- or higher-functional carboxylic acids, alcohols or hydroxycarboxylic acids for the purpose of providing a branch in the polymer for improving the melt viscosity. Examples include polyesters obtained by polymerization.

[0006]

However, these fatty acid polyesters have a glass transition point of less than room temperature and a high crystallinity, and are in a crystalline state at room temperature. Is difficult to suppress, making it opaque and not suitable as a transparent sheet.

For example, Japanese Patent Application Laid-Open No. 6-239014 discloses recording base materials using various biodegradable materials described above, but all of them have difficulty in transparency. In particular, when used as an OHP recording sheet, at least a linear light transmittance of 70% or more is required,
Below this, a clear image cannot be obtained when projected by OHP. Furthermore, OPE, which is currently widely used
Compared with T-sheet, the waist (elastic modulus) is clearly insufficient,
To compensate for this, the thickness must be increased, which results in a further decrease in transparency.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention comprises a water-soluble ink receiving layer (recording layer) and a biodegradable substrate, and has a collapsible and linear light transmittance as a whole. An object of the present invention is to provide a high recording material, particularly a recording material for OHP, and a method for manufacturing the same.

A first feature of the present invention is to provide a hydrophilic polymer compound composed of a repeating unit represented by the following formula (1) or (2) on a substrate made of a polylactic acid-based polymer. A collapsible recording sheet comprising a recording layer as a main component and having a linear light transmittance of 70% or more. -[AY]-(1)-[AYAR]-(2) In the above formulas (1) and (2), A is the following formula (3)

[0010]

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(In the above formula (3), X is a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms. Further, x, y and z are 0 or 1 or more positive numbers, and X is a carbon atom. In the case of a hydrocarbon group having a number of 1 or more, it is represented by the following formula: 44 (x + z) / (molecular weight of α-olefin oxide having 3 or more carbon atoms) y = 80/20 to 94/6. Y is an organic compound residue having two active hydrogens, and R is a dicarboxylic acid compound residue or a diisocyanate compound residue.

A second feature of the present invention is that the base material is a biaxially oriented polylactic acid-based polymer sheet.

Third, co-extrusion of a composition mainly composed of a polylactic acid-based polymer and a hydrophilic polymer compound composed of a repeating unit represented by the above formula (1) or (2). The first or second method for producing a collapsible recording sheet.

A fourth feature is that the obtained sheet is biaxially oriented after the co-extrusion, and there is a third method for producing a collapsible recording sheet.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described.
In the sheet of the present invention, polylactic acid is the most common polylactic acid-based polymer constituting the base material. Polylactic acid having a glass transition point of room temperature or higher is a degradable polymer that can obtain a transparent base sheet, depending on the molding method.

The structural units of polylactic acid include two types of optical isomers, L-lactic acid unit and D-lactic acid unit, and the crystallinity differs depending on the ratio of these two types of structural units. For example, L-
The ratio of lactic acid units to D-lactic acid units is approximately 80: 20-
A 20:80 random copolymer has no crystallinity and becomes a transparent completely amorphous polymer that softens at a glass transition temperature of around 60 ° C. On the other hand, a homopolymer composed of only L-lactic acid units or D-lactic acid units has a glass transition point of 60 ° C.
To a degree, a semi-crystalline polymer having a melting point of 180 ° C. or higher is obtained. This semi-crystalline polylactic acid becomes an amorphous material having excellent transparency by being immediately cooled immediately after being melt-extruded. Further, a more preferable method of obtaining a transparent polylactic acid material is to heat-treat the polylactic acid after uniaxially or biaxially stretching the molecules to orient the molecules. This makes it possible to crystallize while suppressing the growth of spherulites having a size equal to or greater than the wavelength of visible light.

In the present invention, the polylactic acid-based polymer is not only the above-mentioned polylactic acid, but also a copolymer of other hydroxycarboxylic acids and the like to such an extent that the required properties of the polylactic acid are not impaired. You may. Further, the molecular weight may be increased by using a small amount of a chain extender, for example, a diisocyanate compound, an epoxy compound, an acid anhydride or the like. The polylactic acid-based polymer preferably has a weight average molecular weight in the range of 60,000 to 700,000. When it is below this range, practical physical properties are hardly exhibited, and when it is above this, the melt viscosity is too high and the moldability is poor.

The method for producing polylactic acid is not particularly limited, and various known methods such as a condensation polymerization method and a ring-opening polymerization method can be employed. For example, in the condensation polymerization method, L-lactic acid, D
-Lactic acid or a mixture thereof can be directly subjected to dehydration polycondensation to obtain polylactic acid having an arbitrary composition. In the ring-opening polymerization method, lactide, which is a cyclic dimer of lactic acid, can be polymerized in the presence of a selected catalyst using a polymerization regulator or the like, if necessary, to obtain polylactic acid. For lactide,
There are L-lactide which is a dimer of L-lactic acid, D-lactide which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid. These are mixed at an appropriate ratio. Thus, polylactic acid having an arbitrary composition and crystallinity can be obtained. In particular, when polylactic acid is biaxially stretched and then heat-treated to crystallize while maintaining transparency and to suppress heat shrinkage, considering the crystallinity, the L-lactic acid unit and D in the polymer are considered. -The proportion of lactic acid units is
It is preferably in the range of 100: 0 to 94: 6 or 6:94 to 0: 100. Outside this range, a degree of crystallinity sufficient to sufficiently suppress heat shrinkage cannot be obtained.

Any known method can be employed for forming the base sheet. For example, a polymer composition obtained by mixing additives such as a lubricant and an antistatic agent with the above polylactic acid-based polymer, if necessary, is melt-extruded from a T-die and rapidly cooled while being taken up by a rotating casting drum. Then, a solidification method may be used, or an inflation method may be used in which the molten polymer is pulled up from a round die into a cylindrical shape, and while being air-cooled, is simultaneously expanded into a balloon to form a film. In general, the latter has a lower cooling rate, tends to be crystallized, and is disadvantageous to the transparency of the sheet. However, water can be used instead of air to increase the cooling efficiency.

The biaxially oriented substrate sheet is obtained by, for example, stretching a sheet formed by the above-mentioned method using an existing roll-type or tenter-type flat stretching machine or a tubular stretching machine. It is obtained by doing. The stretching temperature is selected within the range from the glass transition temperature to the crystallization temperature of the polylactic acid-based polymer, and the stretching ratio is selected within the range of at least 6 times or less in the uniaxial direction while considering the degree of orientation of the sheet.
To minimize heat shrinkage, use a polylactic acid-based polymer having crystallinity, and keep the sheet under tension for several seconds within the range from the crystallization temperature to the melting point of the sheet after biaxial stretching. The above is obtained by heat treatment.

In the sheet of the present invention, an appropriate hydrophilic polymer is selected from various compounds having an affinity for water as the main component of the water-soluble ink-receiving layer (recording layer). Many of the hydrophilic compounds have a property of being easily soluble in water, and therefore, when the water-soluble ink is placed on the recording layer, there is also a problem that the ink flows out or becomes blurred before fixing. Regarding the fixing property of the ink, it is preferable that the ink is quickly absorbed by the recording layer. Conversely, the one in which the recording layer component is absorbed by the ink has poor fixing property. Therefore, the recording layer is preferably composed of a component having a large molecular weight, that is, a high molecular compound, and it is important that the recording layer is not easily peeled off from the substrate with a small amount of water.

The "recording layer containing a hydrophilic polymer compound as a main component" as used in the present invention is defined as a component among the components constituting the recording layer.
It means that the hydrophilic polymer compound is the largest in weight ratio, preferably 50% or more. The compound contained in the recording layer is not particularly limited as long as it does not inhibit the above-mentioned properties desired for the recording layer. For example, it may contain an inorganic or organic filler, a surfactant, a thickener, and the like.

The hydrophilic high molecular compound (hydrophilic resin) selected in consideration of such points is a hydrophilic high molecular compound composed of a repeating unit represented by the following formula (1) or (2). It is a molecular compound. -[AY]-(1)-[AYAR]-(2) In the above formulas (1) and (2), A is the following formula (3)

[0024]

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(In the above formula (3), X is a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms. Further, x, y and z are 0 or 1 or more positive numbers, and X is a carbon atom. In the case of a hydrocarbon group having a number of 1 or more, it is represented by the following formula: 44 (x + z) / (molecular weight of α-olefin oxide having 3 or more carbon atoms) y = 80/20 to 96/4. Y is an organic compound residue having two active hydrogens, and R is a dicarboxylic acid compound residue or a diisocyanate compound residue.

That is, as shown in the above formula (1) or (2), the repeating unit constituting the hydrophilic polymer compound used in the collapsible recording sheet of the present invention is represented by the following formula:
It contains three types of compound residues, A, Y and R. Among these, the most important one that determines the function of the recording layer is the polyalkylene oxide residue of A.

The weight ratio described above, that is, 44 (x + z)
/ (Molecular weight of α-olefin oxide having 3 or more carbon atoms)
If y is less than 80/20, the hydrophilicity decreases, and the ink absorbency and printability deteriorate. On the other hand, when the ratio exceeds 94/6, the ink becomes poor in bleeding water resistance and the like.
X has a function of imparting hydrophobicity to the polymer compound of the formula (1) or (2), and preferred examples thereof include an alkyl group such as an ethyl group.
By setting the proportions of y and z in the above-mentioned ranges, the hydrophilicity can be maintained and insolubility in water can be achieved.
On the other hand, when X is a hydrogen atom, the whole becomes an ethylene oxide chain, which tends to be excellent in ink absorbency but poor in water resistance.

This high molecular compound is obtained, for example, by subjecting ethylene glycol to addition polymerization of ethylene oxide, then addition polymerization of alkylene oxide, and further reacting a polycarboxylic acid compound or diisocyanate compound with a polyalkylene oxide produced by addition polymerization of ethylene oxide. Can be generated.

The organic compounds having two active hydrogens include ethylene glycol, diethylene glycol,
Examples include propylene glycol, dipropylene glycol, bisphenol A, butylamine, aniline, and polytetramethylene glycol.

The dicarboxylic acid compounds include dicarboxylic acids, dicarboxylic anhydrides, and lower alkyl esters of dicarboxylic acids. Examples of the dicarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, malonic acid, sebacic acid, fumaric acid, adipic acid and the like, and examples of the dicarboxylic acid anhydride include these anhydrides. Examples of the lower alkyl ester of dicarboxylic acid include methyl ester, dimethyl ester, ethyl ester, diethyl ester, and propyl ester of the above-mentioned various dicarboxylic acids.

As the diisocyanate compound,
4,4'-diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, and the like.

The method for producing the sheet of the present invention is not particularly limited as long as a recording layer containing a hydrophilic polymer compound as a main component can be provided on a substrate made of a polylactic acid-based polymer. Various known lamination methods can be employed. Among them, the following methods are important. A hydrophilic polymer compound film, via an adhesive,
A method of laminating a hydrophilic polymer compound and applying it to a substrate sheet. A method of applying the hydrophilic polymer compound to an aqueous solution or an alcohol solution, applying the hydrophilic polymer compound to the substrate sheet, and then drying. A method in which a hydrophilic polymer compound and a polylactic acid-based polymer are melted in separate extruders and then co-extruded to form a laminated sheet.

The glass transition point of the polylactic acid-based polymer is 60 ° C.
At temperatures above this, the sheet may soften and flow through a rubbery state. Since the biaxially oriented polylactic acid-based polymer sheet is crystallized even above this temperature, it does not become rubbery if it is at or below the melting point, but the elastic modulus is still inevitably reduced. In particular, at a temperature of 100 ° C. or higher, the sheet shrinks greatly, and the dimensional stability is poor. Therefore,
It is necessary to laminate the polylactic acid-based polymer sheets in consideration of these drawbacks.

The lamination method can be performed by a so-called wet lamination method or a dry lamination method. As the adhesive at the time of lamination, vinyl-based, acrylic-based, polyamide-based, polyester-based, urethane-based, and rubber-based adhesives are used. Normally, when laminating with a laminator, the sheet is preheated before lamination, and after lamination, it is often aged to dry the solvent and cure the adhesive, but the sheet softens. The heating temperature for preheating or aging needs to be 80 ° C. or less so as not to lose the flatness or shrink. In addition, when the recording layer is made extremely thin, if the hydrophilic polymer film unwound during lamination has no strength or stiffness, the film may be broken when stretched or stretched and cannot be laminated precisely. Be careful as there are.

In the laminating method, a hydrophilic polymer compound is melted by an extruder or the like and extruded into a film shape, and the roll is pressure-bonded to a rolled-out polylactic acid-based polymer base sheet, or This is a method of thermocompression bonding and bonding. It is important that the temperature of the hydrophilic polymer compound film at the time of lamination does not exceed 80 ° C. If the temperature is higher than this, there is a possibility that the base sheet may be deformed similarly to the case described above.

In the laminating method, a hydrophilic polymer compound solution is sprayed from a nozzle onto a polylactic acid-based polymer sheet, preferably a biaxially oriented sheet, or is applied by a roller, and then the sheet is dried. . It is preferable that the drying temperature at this time does not exceed 80 ° C. In the case of an aqueous solution, drying at a temperature of 80 ° C. or less requires a long time, and drying in a reduced pressure is required for finishing in a short time, which is disadvantageous in the process. From the viewpoint of facilitating drying, it is preferable to use a low boiling point solvent such as alcohol.

In the laminating method, a polylactic acid-based polymer for forming a base material and a hydrophilic polymer compound for forming a recording layer are melted by separate extruders, respectively, and then guided into the same conduit, and then are melted. Known methods such as a so-called feed block method of obtaining a sheet by extrusion and a so-called multi-manifold method of guiding and extruding each molten resin into a die separated into two layers can be employed. However, many of the general-purpose hydrophilic polymer compounds are formed into a film by a so-called wet method, and those that can be melt-extruded are limited. Further, at present, there is almost no recording layer having excellent properties as described above. An important point in the present invention is that the hydrophilic polymer compound composed of the repeating units represented by the above formulas (1) and (2) is
It is melt extrudable and has excellent properties as a recording layer, and has been found to produce a laminated sheet by co-extrusion of these.

Further, a useful point of the hydrophilic high molecular compound used in the present invention is that a laminated sheet with a substrate made of a polylactic acid-based polymer can be stretched and heat-treated as it is,
The advantage is also obtained with respect to the manufacturing method of (1). When the laminated sheet obtained by co-extrusion is stretched by a tenter or the like, it is necessary to use a hydrophilic polymer compound that can be stretched and heat-treated under the same conditions as the polylactic acid-based polymer as the base material. . That is, the temperature at which the polylactic acid-based polymer is stretched is set at 50 to 90 ° C, preferably 60 to 80 ° C. At this temperature, the hydrophilic polymer compound layer also softens and becomes rubbery or molten. Then, it must be semi-liquid and capable of following the stretching of the substrate. When the polylactic acid-based polymer is oriented, heat treatment may be performed immediately after stretching for the purpose of heat setting. The temperature is usually set between the glass transition point and the melting point of the polymer,
In the highest case, it may be exposed to a temperature of about 180 ° C. for several seconds. At this time, if the hydrophilic polymer compound layer is easily decomposed, it is difficult to produce a laminated film by this method.

The hydrophilic polymer compound comprising the repeating units represented by the above formulas (1) and (2) used in the present invention has a melting point of about 60 ° C., and under the conditions at the time of stretching. It melts easily and can follow the stretching of the polylactic acid-based polymer as the base material. Although not particularly limited in this respect, as the hydrophilic polymer compound, a compound having a large molecular weight, that is, a compound having a high melt viscosity is more advantageous. If the viscosity is too low, the hydrophilic polymer compound layer will flow during stretching, resulting in a sheet having low thickness accuracy and poor appearance. In addition, all of the hydrophilic polymer compounds used in the present invention have a decomposition temperature of 200 ° C. or higher, are easily decomposed under heat treatment conditions, and do not deteriorate appearance.

When high water resistance is required depending on the conditions of use of the sheet of the present invention, the hydrophilic polymer compound layer is irradiated with ionizing radiation or ultraviolet light,
Crosslinking is preferred. By the irradiation, the hydrophilic polymer compound is crosslinked, and the strength in a state containing water is improved. In addition, the crosslinked portion retains hydrophilicity and has good ink absorbability, but the ink dries faster, and clear recording can be performed while controlling the flow of the different color ink. Examples of ionizing radiation include electron beams,
γ-rays, X-rays and the like can be used. Irradiation is preferably performed in a substantially oxygen-free state, such as by substituting with an inert gas such as nitrogen. The dose of ionizing radiation is preferably in the range of 0.5 to 20 Mrad in terms of absorbed dose.

In the sheet of the present invention, the linear light transmittance must be 70% or more. If it is less than this, a clear image cannot be obtained when projected by OHP.
Thus, here, the linear light transmittance is, as incident light,
The ratio of the amount of transmitted light to the amount of incident light when a parallel light beam perpendicular to the sample sheet surface is used is determined by JISK
It was measured according to 7105. Generally, light transmittance is divided into linear transmittance and diffuse transmittance, and these are collectively referred to as total transmittance. Of these, diffuse transmission refers to transmission of incident light without depending on the refractive index of a normal medium. Therefore, even if the sheet is entirely transparent and has a high diffuse transmittance, a problem such as blurring of an image occurs even when the sheet is projected by the OHP, and the entire image becomes unclear.

[0042]

The present invention is not limited by the following examples. The measurement and evaluation of the physical properties of the recording sheet obtained in the examples were performed under the following conditions.

(1) Linear light transmittance The measurement was performed according to JIS K 7105. The larger the value, the better the transparency.

(2) Inflow of ink Printing was performed with black ink using an ink jet printer. It was visually observed to determine whether or not ink had flowed out on the recording sheet surface. When the ink flow did not occur and the ink flow did not occur, x indicates that the ink flow did not occur, and when the ink flow did not occur, the character was blurred.

(3) Stickiness of Printed Image in High Humidity Atmosphere The sheet printed in (2) was left in an atmosphere of 30 ° C. × 95% RH for 24 hours. Thereafter, the user touched the surface of the recording sheet to determine the presence or absence of tackiness.

(4) OHP aptitude Using an overhead projector (OHP),
The recorded image printed in (2) was projected on a screen, and OHP suitability was determined by visual observation. When the unprinted portion was bright and the balance with the print was clear and easy to see, the unprinted portion was dark, and when the printed portion was not clearly displayed, the cross was marked X.

The hydrophilic high molecular compound used in the following examples was produced as follows. (Production Example 1) After addition polymerization of ethylene glycol with ethylene oxide, butylene oxide was addition-polymerized, and ethylene oxide was further addition-polymerized to obtain a polyalkylene oxide polymer compound (PAO: weight-average molecular weight 15.0).
00). This compound is represented by the above formula (1), and X, x, y and z in the formula (3) are as follows. X = ethyl group, x = 69, y = 21, z = 69 The weight ratio calculated from x, y, z is 44 (x +
z) / 72y = 80/20.

(Preparation Example 2) To 100 parts by weight of the polyalkylene oxide polymer compound prepared in Preparation Example 1, 1.4 parts by weight of dimethyl terephthalate was added, and a transesterification reaction was carried out to perform a hydrophilic polymer compound (EE1: weight average). Molecular weight 1
30,000). This compound is composed of the repeating unit represented by the formula (2), and Y and R in the formula (2) are as follows.

[0049]

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(Production Example 3) After addition polymerization of ethylene oxide to ethylene glycol, an α-olefin oxide (a mixture of epoxide compounds having 12 and 14 carbon atoms, molecular weight 196) was addition-polymerized, and further ethylene oxide was addition-polymerized. 1.9 parts by weight of dimethyl sebacate is added to a polyalkylene oxide compound (weight average molecular weight of about 13,000), and transesterification is performed to perform a hydrophilic polymer compound (EE2: weight average molecular weight of 120,000).
I got

The present compound is composed of the repeating unit represented by the formula (2), and comprises Y and R in the formula (2) and X, x, y and z in the formula (3). Are as follows, respectively. _{Y: -OCH 2 CH 2 O- R} : -OC (CH 2) 8 CO- X: the mixing ratio in the mixing of the alkyl group of the alkyl group and 12 carbon atoms 10 carbon atoms (weight ratio) as follows. (Alkyl group having 10 carbon atoms / alkyl group having 12 carbon atoms = 56/4
4) x = 56, y = 2, z = 84 The weight ratio calculated from x, y, z is 44 (x +
z) / 196y = 94/6. The weight ratio z / (x + z) calculated from x and z was 60%.

(Example 1) Polylactic acid (manufactured by Shimadzu Corporation, trade name: Lacty 1000, weight average molecular weight: about 20)
The ratio of L-lactic acid units and D-lactic acid units in the polymer is 9
9: 1) was melt-extruded using a 30 mmφ small single-screw extruder, and then taken off while being rapidly cooled by a casting drum having a surface temperature of 57 ° C. to produce a sheet having a thickness of 100 μm. The produced sheet was subjected to an energy of 25 W / m ² /
After the corona treatment for 2 minutes, a 2μ thick urethane
m and aged at 40 ° C. for 6 hours.

The hydrophilic polymer compound (PAO) prepared in Preparation Example 1 was adjusted to a 50% by weight methanol solution on the surface of the polylactic acid sheet which was subjected to easy adhesion treatment, and the thickness after drying was 3 μm. And then dried in an oven at 60 ° C. for 1 hour.
Aging was performed at ℃ for 1 day to obtain a recording sheet. Table 1 shows the evaluation results.

Example 2 The hydrophilic polymer compound (EE1) produced in Production Example 2 and the polylactic acid used in Example 1 were charged into different 40 mmφ single-screw extruders, and the same multi-manifold was used. Lead to the formula T-die, 2
Layer co-extrusion was performed to produce a laminated sheet. The extrusion temperature was 200 ° C. in both cases, and the thickness was such that the thickness of the hydrophilic polymer compound recording layer was about 5 μm and the thickness of the polylactic acid base layer was 100 μm. Table 1 shows the evaluation of the obtained sheet.

Example 3 A laminated sheet having a hydrophilic polymer compound recording layer thickness of about 30 μm and a polylactic acid base material layer thickness of about 500 μm was prepared in the same manner as in Example 2. The film was stretched 2.3 times at 75 ° C. in the machine direction, and then stretched 2.5 times at 70 ° C. by a tenter in the width direction.
After stretching, heat treatment is performed in a heat treatment zone of a tenter at a temperature of 130 ° C. for a treatment time of 30 seconds, and a total thickness of about 90 μm (including a recording layer of about 5 μm) is based on biaxially oriented polylactic acid.
Was obtained. Table 1 shows the evaluation of the obtained sheet.

Example 4 Polylactic acid alone was melt-extruded, stretched and heat-treated under the same conditions as in Example 3 to a thickness of about 100.
A μm biaxially oriented polylactic acid sheet was prepared. On one surface of this sheet, a 2 μm-thick easily-adhesive urethane-treated layer was provided by the method described in Example 1.

On the other hand, the hydrophilic polymer compound (EE2) produced in Production Example 3 was converted to 14
The mixture was melt-extruded from a T-die at 0 ° C. and led to a cast roll set at a temperature of 45 ° C. to form a film. At this time, it was laminated on a biaxially oriented polylactic acid sheet by a so-called extrusion lamination method. That is, before the extruded hydrophilic polymer compound is cooled and solidified by the cast roll, the biaxially oriented polylactic acid sheet is unwound, and the surface opposite to the cast roll surface of the hydrophilic polymer compound film is formed on the polylactic acid sheet. So that the surfaces treated for easy adhesion overlap each other, and were pressure-bonded with a roll. The recording layer of the hydrophilic polymer compound of the recording sheet obtained by this method had a thickness of 7 μm. Table 1 shows the evaluation of the obtained sheet.

Example 5 The recording sheet prepared in Example 3 was irradiated with γ-rays at an absorbed dose of 10 Mrad to obtain a recording sheet in which the hydrophilic polymer compound of the recording layer was crosslinked.

Comparative Example A hydrophilic polymer was prepared in the same manner as in Example 2, except that polybutylene succinate adipate (Showa Polymer Co., Ltd., trade name: Bionore # 1001) was used instead of polylactic acid. Compound recording layer thickness about 5 μm, polybutylene succinate base material layer thickness 100
A μm coextruded laminated sheet was produced.

[0060]

[Table 1]

The recording sheets of Examples 1 to 5
High transparency and excellent OHP characteristics. Above all, it can be seen that Examples 2 to 5 have excellent ink fixability and are hardly stained. In particular, the sheet obtained in Example 5 has high water resistance even under high humidity, and is the most excellent recording sheet in Examples. On the other hand, in the comparative example, it can be seen that the transparency of the base material was low and there was no OHP suitability.

[0062]

According to the present invention, it has the characteristic of disintegrating in a natural environment, is excellent in transparency, has good ink absorbency, runs out of printed ink, and blurs a printed screen under high humidity. It is possible to obtain a disintegratable recording sheet which is not sticky and has excellent ink jet recording characteristics.

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Claims (4)

[Claims] 1. A recording layer mainly composed of a hydrophilic polymer compound composed of a repeating unit represented by the following formula (1) or (2) is provided on a substrate made of a polylactic acid-based polymer. A disintegrable recording sheet comprising a linear light transmittance of 70% or more. -[AY]-(1)-[AYAR]-(2) In the above formulas (1) and (2), A is the following formula (3): (In the above formula (3), X is a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms. In addition, x, y, and z are 0 or 1 or more positive numbers, and X is 1 or more carbon atoms. In the case of a hydrocarbon group represented by the following formula, the poly is represented by the following formula: 44 (x + z) / (molecular weight of α-olefin oxide having 3 or more carbon atoms) y = 80/20 to 94/6.) Y is an organic compound residue having two active hydrogens, and R is a dicarboxylic acid compound residue or a diisocyanate compound residue. 2. The disintegratable recording sheet according to claim 1, wherein said base material is a biaxially oriented polylactic acid polymer sheet. 3. A method comprising co-extruding a composition mainly composed of a polylactic acid-based polymer and a hydrophilic polymer compound composed of a repeating unit represented by the above formula (1) or (2). The method for producing a disintegratable recording sheet according to claim 1 or 2, wherein 4. The method according to claim 3, wherein the obtained sheet is biaxially oriented after the co-extrusion.