JP2797902B2 - Silicone composition for release agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an addition-reaction type solvent-type release agent which has excellent curability, has a small decrease in residual adhesiveness, and provides a release silicone cured film having excellent air exposure resistance. The present invention relates to a silicone composition for use.

[0002]

2. Description of the Related Art
For the purpose of preventing adhesion or sticking between a substrate such as paper and plastic film and an adhesive substance, a cured film of a silicone composition is formed on a substrate surface to impart releasability. ing.

In this case, a method of forming a silicone film on the surface of a base material includes (1) an addition reaction of an organopolysiloxane containing an aliphatic unsaturated group with an organohydrogenpolysiloxane using a platinum compound as a catalyst. There are known a method of forming a peelable film by performing a condensation reaction of an organopolysiloxane using an organic acid metal salt catalyst such as an organotin compound, and the like.

[0004] The silicone compositions used in these methods are all so-called heat-cure types in which a film is formed by heating, and depending on the properties thereof, those which are dissolved in an organic solvent such as toluene or the like, are emulsified. Emulsion type and solventless type consisting of silicone only.

[0005] From the viewpoint of productivity, the release film formed by the first method, which has a higher curing speed than the second method, is widely used. When exposed to the inside, it is difficult to peel off the adhesive product from the substrate, and in extreme cases, there is a problem that the adhesive product does not peel off from the substrate. This is presumed to be due to dust in the air adhering to the cured silicone film, and this exposure to air is also a factor in the stable production of adhesive products and the repeated use of substrates with a cured silicone film. It is becoming important.

In general, a cured film composed of an addition-reaction type silicone composition is inferior in air exposure resistance to a cured film composed of a condensation reaction type silicone composition. The cured film has a lower air exposure resistance than a film composed of an emulsion-type or solvent-free composition.

Accordingly, in a silicone composition of the addition reaction type solvent type, a component having no reactive substituent (so-called migration component) is excessively added, and dust adhering to a cured film formed from this composition is removed by the migration component. A method of improving the air exposure resistance of the cured silicone film by incorporating it into the air has also been adopted, but in this case, problems such as transferability such as roll contamination and poor printing, and extremely low adhesive strength of the pressure-sensitive adhesive There is a problem that causes disadvantages.

[0008] The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a silicone composition for an addition-reaction type solvent-type release agent which has excellent curability, has a small decrease in residual adhesiveness, and provides a release silicone cured film excellent in air exposure resistance. I do.

[0009]

The present inventors have conducted intensive studies in order to achieve the above object. As a result, (A) a vinyl group in one molecule contained 0.15 to 3 moles of all organic groups. %
A diorganopolysiloxane having a viscosity of 1,000 to 100,000 centipoise at 25 ° C. of a 30% by weight toluene solution, (B) having at least three hydrogen atoms bonded to silicon atoms in one molecule, R ₂ SiO units (where R is the same or different monovalent hydrocarbon group)
５０50 mol%, and S based on the vinyl group of the component (A)
By adding an organohydrogenpolysiloxane having an iH group amount of 2 to 5 in molar ratio and (C) a platinum group metal-based catalyst, an addition reaction can be performed as compared with a conventional addition-reaction-type solvent-type silicone composition. Because of its excellent properties, the amount of residual functional groups (vinyl groups) in the cured film obtained from this composition can be reduced, and therefore, the possibility of dust adhesion due to charging of the vinyl groups is reduced, In addition, since the cured film is hard (rubber hardness according to Asker hardness meter is 55 to 85), it is possible to prevent dust from entering the cured film, and to provide a cured film having significantly improved air exposure resistance. Therefore, it is possible to prevent heavy peeling trouble due to air exposure of the base material on which the silicone cured film is formed at the time of adhesive processing and the like, and it is possible to improve the quality control of productivity. And finding the door, the present invention has been accomplished.

Accordingly, the present invention relates to (A) a polymer containing 0.15 to 3 mol% of vinyl groups with respect to all organic groups in one molecule;
0% by weight toluene solvent has a viscosity at 25 ° C. of 1,000
A diorganopolysiloxane of 0 to 100,000 centipoise, (B) having at least three hydrogen atoms bonded to a silicon atom in one molecule, and having an R ₂ SiO unit (here, R
Is the same or different monovalent hydrocarbon group) from 10 to 50 mol%
(A) an organohydrogenpolysiloxane having a molar ratio of SiH groups to vinyl groups of component (A) of from 2 to 5; and (C) a platinum group metal-based catalyst. Provided is a silicone composition for a release agent, which is 55 to 85 in total.

Hereinafter, the present invention will be described in more detail.
The diorganopolysiloxane of the component (A) contains 0.15 to 3 mol%, particularly preferably 0.2 to 2 mol%, of vinyl groups based on all organic groups in one molecule, and a 30% by weight toluene solution. The viscosity at 25 ° C. is 1,000 to 100,00
0 centipoise (cp).

If the dioxane polysiloxane has a vinyl group content of less than 0.15 mol%, the curability is poor,
Since the obtained cured film is relatively soft, the desired excellent air exposure resistance cannot be obtained. On the other hand, when the vinyl group content exceeds 3 mol%, the peel resistance increases, and excellent peel performance cannot be obtained. Further, the viscosity of the 30% by weight toluene solution at 25 ° C. is 1,000 cp.
If it is lower than this, there is a disadvantage in dissolving the organopolysiloxane in toluene, and if it is higher than 100,000 cp, it is difficult to synthesize such organopolysiloxane.

In the diorganopolysiloxane of the component (A), examples of the organic group other than the vinyl group include an alkyl group such as a methyl group, an ethyl group and a propyl group, and an aryl group such as a phenyl group and a tolyl group. However, it is preferable that 80 mol% or more is a methyl group from the viewpoint of improving curability and releasability. In addition, the terminal of the molecular chain of this diorganopolysiloxane may be any of a hydroxyl group, an alkyl group, a vinyl group, etc., but is preferably a vinyl group from the viewpoint of curability, and the molecular shape is linear. However, it may be branched.

The organohydrogenpolysiloxane of the component (B) has at least three hydrogen atoms bonded to a silicon atom in one minute, and has an R ₂ SiO unit (R is the same or different monovalent hydrocarbon). ), And the SiH group and the vinyl group in the component (A) undergo an addition reaction to form a cured film.

Here, R may be an alkyl group such as a methyl group, an ethyl group or a propyl group, or an aryl group such as a phenyl group or a tolyl group, and is a methyl group from the viewpoint of improving the rate of the addition reaction. Is preferred.

Further, other organic groups other than the hydrogen atom bonded to the silicon atom are the same as the above-mentioned R, but 90% by mole thereof
The above is preferably a methyl group.

Examples of such an organohydrogenpolysiloxane include those represented by the following formulas (1) and (2).

[0018]

Embedded image

In the above equation, n / (m + n) and q /
(P + q) is 0.1 to 0.5, especially 0.2 to 0.5
It is preferred to be in the range of 0.5. If n / (m + n) and q / (p + q) are less than 0.1, it is difficult for the organopolysiloxane to effectively react with the vinyl group, so that the excellent air exposure resistance, which is the object of the present invention, cannot be obtained. , N / (m + n) and q / (p + q) exceeding 0.5 may have a disadvantage that the air exposure resistance is good but the adhesion to the substrate is poor.

The organohydrogenpolysiloxane of the component (B) may be linear or branched, and preferably has a viscosity at 25 ° C. of 10 to 1,000 cp.

The compounding amount of the component (B) may be determined according to the amount of the vinyl group contained in the component (A). From the viewpoint of the cured film forming property and the peeling performance, the ratio of SiH / SiCH = CH ₂ is determined. It is necessary to be 2 to 5, especially 2.5 to 4.5.
It is preferable that When the ratio is less than 2, the cured film becomes relatively soft, so that the resistance to exposure to air deteriorates. When the ratio exceeds 5, the peeling resistance increases.

The platinum group metal-based catalyst of the component (C) is (A)
A catalyst for accelerating the addition reaction between the component and the component (B), and any known addition reaction catalyst can be used. Examples of such platinum group metal-based catalysts include, for example, platinum-based, palladium-based, and rhodium-based catalysts, and among them, platinum-based catalysts are particularly preferable. Examples of such platinum-based catalysts include chloroplatinic acid, alcoholic and aldehyde solutions of chloroplatinic acid, and complexes of chloroplatinic acid with various olefins or vinylsiloxane.

The amount of the platinum group metal-based catalyst added is a catalytic amount, but from the viewpoint of obtaining a good cured film and from an economic viewpoint, 100 parts by weight of the component (A) (parts by weight, hereinafter the same) is used. The amount of metal is preferably in the range of 1 to 1,000 ppm.

The composition of the present invention includes the above (A) to (C)
It is obtained by blending a predetermined amount of the component, in addition to the above components, other optional components, for example, for the purpose of suppressing the catalytic activity of the platinum group metal-based catalyst, various organic nitrogen compounds,
Requires an activity inhibitor such as organophosphorus compounds, acetylene compounds, oxime compounds, and organic chloro compounds, and diorganopolysiloxanes that do not have hydrogen atoms or vinyl groups bonded to silicon atoms for the purpose of controlling peeling force. It can be added accordingly. In addition, the addition amount of the optional component can be a normal amount as long as the effect of the present invention is not impaired.

In preparing the silicone composition of the present invention, it is preferable to mix the components (A), (B) and optional components uniformly before adding the component (C). They may be used or two or more of them may be used in combination. Also,
If necessary, it may be dissolved in an organic solvent such as toluene, xylene or n-hexane.

The silicone composition thus prepared is applied to a substrate such as paper or plastic film and then cured by heating in a conventional manner. The Asker C hardness of the cured film formed by heat curing is 55 to 85.
Therefore, the substrate on which the cured film of the composition of the present invention is formed is suitably used as a release paper or the like.

[0027]

Industrial Applicability The silicone composition of the present invention has excellent curability, has a small decrease in residual adhesiveness, and gives a silicone cured film having excellent air exposure resistance, and is excellent as a release agent. It has excellent performance.

[0028]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. All parts in each example are parts by weight, and the viscosity is a value at 25 ° C.

The curability, peel strength, residual adhesion, exposure to air, and cured film hardness of the silicone composition were measured by the following methods.

A predetermined amount of the curable silicone composition is applied to the surface of a thin film or sheet-like substrate, and the cured film formed by heating in a hot air dryer at a predetermined temperature is rubbed several times with a finger. And the time until no drop-off occurred.

Peeling Force A predetermined amount of the silicone composition is applied to the surface of a thin film or sheet-like substrate and heated in a hot air drier at a predetermined temperature to form a cured film. A solvent-based adhesive, Olivain BPS-5127 (manufactured by Toyo Ink Mfg. Co., Ltd.) was applied and heat-treated at 100 ° C. for 3 minutes. Next, a high-quality paper having a basis weight of 64 g / m ² was bonded to the treated surface and aged at 25 ° C. for 20 hours. Then, the sample was cut into a width of 5 cm, and the sample was cut with a tensile tester.
The force (g) required for pulling the bonded paper at an angle of 80 degrees at a peeling speed of 0.3 m / min and at a speed of 60 m / min to peel was measured.

Residual adhesive strength A polyester tape (trade name: Lumirror 31B, manufactured by Nitto Denko Corporation) is adhered to the surface of the cured silicone composition film formed on the substrate surface in the same manner as in the case of the measurement of the peeling force. A load of 20 g / cm ² is applied at 70 ° C. for 20 minutes.
After aging for a time, the tape was peeled off and attached to a stainless steel plate. Next, remove this tape from the stainless steel plate
Peeling was performed at an angle of 80 degrees at a peeling speed of 0.3 m / min, and the force (g) required for peeling was measured. Further, the force (g) required for peeling the tape, which was bonded to a Teflon plate as a blank and treated in the same manner from the stainless steel plate, was measured. These ratios were expressed as percentages.

Exposure resistance to air Exposure of the cured film of the silicone composition formed on the surface of the substrate in the same manner as in the case of the peeling force measurement was performed in the room for 3 to 16 hours, and then the peeling force was measured in the same manner. The force (g) required for peeling at a peel speed of 0.3 m / min was measured,
The change in peeling force due to air exposure was examined.

Cured Film Hardness The silicone composition is heated in a hot air dryer at a predetermined temperature for a predetermined time to form a rubber cured film having a predetermined thickness. Co., Ltd.)
Was used to measure the hardness of the cured film.

Example 1 Both ends of a molecular chain were blocked with a dimethylvinylsiloxy group, containing 3 mol% of a methylvinylsiloxane unit, and having a 30%
100 parts of 0 cp dimethylpolysiloxane (the content of vinyl groups to all organic groups is 1.5 mol%) is dissolved in 2,000 parts of toluene, and both ends of the molecular chain are blocked with trimethylsiloxy groups. 9.2 parts of methylhydrogenpolysiloxane containing 25 mol% of siloxane units and having a viscosity of 45 cp (SiH / SiCH =
CH ₂ = 2.5) and 3 parts of 1,1-dimethyl-2-propenyloxytrimethylsilane were further added, and the mixture was stirred until the mixture became uniform. 200pp in conversion
m to obtain a silicone composition.

Next, the resulting silicone composition Polyethylene laminated paper (basis weight 100 g / m ²⁾ in at solids 0.7~0.8g / m ² was applied, and 100 as a sample for curing test The sample was subjected to a heat treatment at 140 ° C. for 30 seconds at 140 ° C., and a cured film was formed. Furthermore, thickness is 12m
After the toluene was air-dried at 25 ° C. for 20 hours so as to obtain m, a rubber sheet was prepared by heating at 120 ° C. for 20 minutes, and the Asker C hardness was measured as a sample for measuring a cured film hardness. Table 1 shows the measurement results.

Example 2 Instead of the dimethylpolysiloxane used in Example 1, the molecular chain ends were blocked with dimethylvinylsiloxy groups, containing 0.5 mol% of methylvinylsiloxane units and a 30% toluene dissolution viscosity. Is 10,
Dimethylpolysiloxane having a vinyl group content of 0.25 mol% with respect to all organic groups
Parts, the amount of methyl hydrogen polysiloxane used in Example 1 was 5.5 parts (SiH / SiCH = CH ₂ =
A silicone composition was prepared in the same manner as in Example 1 except that 4.5) was used, and the same physical property test as in Example 1 was performed.
The results are also shown in Table 1.

Example 3 Instead of the dimethylpolysiloxane used in Example 1, the molecular chain ends were blocked with dimethylvinylsiloxy groups, containing 1.2 mol% of methylvinylsiloxane units, and a 30% toluene dissolution viscosity. Is 4,5
85 cp of dimethylpolysiloxane having a content of 00 cp (the content of vinyl groups with respect to all organic groups is 0.6 mol%), and both ends of molecular chains are blocked with trimethylsiloxy groups, and 30%
15 parts of dimethylpolysiloxane having a toluene dissolution viscosity of 20,000 cp was used, and the blending amount of methylhydrogenpolysiloxane used in Example 1 was 4.4 parts (SiH / SiCH = CH ₂ = 3.5) A silicone composition was prepared in the same manner as in Example 1 except that the test was performed, and the same physical property test as in Example 1 was performed. The results are also shown in Table 1.

COMPARATIVE EXAMPLE 1 The blending amount of methyl hydrogen polysiloxane used in Example 1 was 5.5 parts (SiH
/ SiCH = CH ₂ = 1.5) to prepare a silicone composition in the same manner as in Example 1.

Comparative Example 2 Instead of the methylhydrogenpolysiloxane used in Example 1, 6.4 parts of methylhydrogenpolysiloxane having a viscosity of 20 cp and having both ends of the molecular chain blocked by a trimethylsiloxy group ( Si
H / SiCH = CH ₂ = 2.5) A silicone composition was prepared in the same manner as in Example 1 except for blending, and the same physical property test as in Example 1 was performed. The results are also shown in Table 1.

COMPARATIVE EXAMPLE 3 Instead of the methyl hydrogen polysiloxane used in Example 1, both ends of the molecular chain were blocked with trimethylsiloxy groups, and methyl having 60 mol% of dimethylsiloxane units and a viscosity of 150 cp was used. 16.0 parts of hydrogen polysiloxane (SiH / S
iCH = CH ₂ = 2.5) A silicone composition was prepared in the same manner as in Example 1 except for blending, and the same physical property test as in Example 1 was performed. The results are also shown in Table 1.

Comparative Example 4 The compounding amount of methyl hydrogen polysiloxane used in Example 1 was 22.1 parts (Si
A silicone composition was prepared in the same manner as in Example 1 except that H / SiCH = CH ₂ = 6), and the same physical property test as in Example 1 was performed. The results are also shown in Table 1.

[0043]

[Table 1]

Claims (1)

(57) [Claims] 1. (A) One molecule contains 0.15 to 3 mol% of vinyl groups based on all organic groups, and a 30% by weight toluene solution has a viscosity at 25 ° C. of 1,000 to 100,000.
0 centipoise diorganopolysiloxane, (B) 1
At least three hydrogen atoms bonded to silicon atoms in the molecule
And contains 10 to 50 mol% of R ₂ SiO units (where R is the same or different monovalent hydrocarbon group), and the amount of the SiH group to the vinyl group of the component (A) is 2 in a molar ratio. A silicone composition for a release agent, comprising an organohydrogenpolysiloxane of (C) to (C) and a platinum group metal-based catalyst (C), and having a rubber hardness after curing of from 55 to 85 as measured by an Asker hardness meter.