JPH0420570A - Silicone rubber composition excellent in peelability - Google Patents

Abstract

PURPOSE:To prepare the title compsn. easily peelable at low and high speeds and giving a peeled film having a high residual adhesion rate by compounding an organopolysiloxane, an organohydrogenpolysiloxane, an arylated organopolysiloxane, and a specific catalyst. CONSTITUTION:The title compsn. is prepd. by compounding an organopolysiloxane with a viscosity at 25 deg.C of 50cP having no aryl group and at least two alkenyl groups directly attached the Si atoms in the molecule; an organohydrogenpolysiloxane having no aryl group and at least two H atoms directly attached to the Si atoms in the molecule; an organopolysiloxane of the formula (wherein R is H, alkenyl, alkyl, or aryl provided that at least one of Rs is H or alkenyl and that 0.5-30mol% of total Rs are aryl; and X is a positive integer) having a viscosity at 25 deg.C of 50-1000000cP; and a platinum catalyst (e.g. a chloroplatinic acid). The compsn. is easily peelable at low and high speeds and gives a peeled film having a high residual adhesion rate of a peeled self-adhesive sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a silicone composition with excellent releasability. The present invention relates to a silicone composition for release paper that provides a release film that exhibits a high residual adhesion rate on adhesive sheets and the like.

(Prior art) Conventionally, a film of a silicone composition has been formed on the surface of the substrate in order to prevent adhesion or sticking between the substrate such as paper, processed paper, plastic film, etc. and the adhesive sheet. Imparting mold releasability has been done.

In this case, the method for forming a silicone film on the surface of the substrate is as follows: 1. Using a platinum-based compound as a catalyst, an organopolysiloxane containing an aliphatic unsaturated group and an organohydrodiene polysiloxane are subjected to an addition reaction to improve mold releasability. A method of forming a film, and a method of forming a releasable film by subjecting organopolysiloxane to a condensation reaction using an organic acid metal salt catalyst such as an organic tin compound are known. The silicone compositions used in these methods are all called heat-cure types that form a film by heating, and depending on their properties, there are two types: solvent type, which is dissolved in an organic solvent such as toluene, and emulsion type, which is made into an emulsion. , is classified as a solvent-free type consisting only of silicone.

Furthermore, a silicone composition for release paper to which a non-functional organopolysiloxane containing an aryl group is added is known (Japanese Unexamined Patent Publication No. 60-133051), and this silicone composition has easy peelability during high-speed peeling. It has excellent properties and is said to be useful for improving workability in the unwinding process in the production of adhesive paper, the scum removal process in the production of adhesive labels, the label pasting process, etc.

(Problems to be Solved by the Invention) However, although the silicone composition for release paper to which a non-functional organopolysiloxane containing an aryl group is added has excellent release properties, There was a disadvantage in that the residual adhesion rate of the peeled pressure-sensitive adhesive sheet was significantly reduced due to blooming of the polysiloxane. That is, there is a problem in that the adhesiveness of the peeled pressure-sensitive adhesive sheet is significantly lower than that of an unused pressure-sensitive adhesive sheet.

The present invention has been made in view of the above circumstances, and provides a silicone composition for release paper that provides an excellent release film that is easy to release during low-speed and high-speed peeling and has little reduction in the residual adhesion rate of the peeled pressure-sensitive adhesive sheet. The purpose is to provide

(Means for Solving the Problems) That is, according to the present invention, (A) has a viscosity at 25° C. of 50 centivoids or more, does not contain an aryl group in its molecule, and has at least 2 aryl groups in each molecule; (B) an organopolysiloxane in which an alkenyl group of Diene polysiloxane, (C) the following formula, R35iO(RzSiO) At least one of R is a hydrogen atom or an alkenyl group, 0.5 to 30 mol% of all R is an aryl group, χ is a positive integer, and the viscosity at 25 ° C. is 50~1.000,
000 centivoise; and (D) a platinum group metal catalyst. Organopolysiloxane does not contain an aryl group in its molecule and contains an alkenyl group as an organic group bonded to a silicon atom.

That is, when using an organopolysiloxane containing an aryl group such as a phenyl group or tolyl group in the molecule, there is a disadvantage that, for example, it is not possible to achieve a significant reduction in the peeling force of the adhesive sheet to be peeled off. arise.

Further, the alkenyl group is contained in two or more in one molecule,
In particular, 0.05 to 5 per total organic group bonded to silicon atoms.
It is desirable that the content is 0 mol%, more preferably 0.2 to 10 mol%. If the alkenyl group content is too low, a substantial curing rate may not be obtained, and if the alkenyl group content is too large,
Not only is it difficult to synthesize, it has no advantages in terms of properties, and it is also uneconomical from an industrial standpoint. Examples of such alkenyl groups include vinyl groups and allyl groups, with vinyl groups being particularly preferred.

Organic groups other than vinyl groups bonded to silicon atoms include:
Examples include alkyl groups such as methyl, ethyl, and propyl groups, and monovalent hydrocarbon groups in which part or all of the hydrogen atoms bonded to these carbon atoms are substituted with halogen atoms, cyano groups, and the like. In particular, it is preferable that 50 mol% of organic groups other than alkenyl groups bonded to silicon atoms be methyl groups based on the total organic groups.

This organopolysiloxane is desirably substantially linear, and its terminal end may be an organic group such as a hydroxyl group, a vinyl group, or a methyl group, but preferably a vinyl group.

Further, the above-mentioned organopolysiloxane has a viscosity of 50 cp (centipoise) or more at 25° C. from the viewpoint of the performance of the film formed, and may be either oil-like or rubber-like.

B Organohydrodiene polysiloxane The organohydrodiene polysiloxane used in the present invention as the component (B) acts as a crosslinking agent, and the SiH group in its molecule acts as a crosslinking agent for the organopolysiloxane as the component (A). A cured film is formed by addition to an alkenyl group bonded to a silicon atom.

Moreover, this organohydrodiene polysiloxane has 1
At least 2 hydrogen atoms bonded to silicon atoms in the molecule
, preferably 3 or more. This is because the presence of such hydrogen atoms can act as a crosslinking agent.

The organic group bonded to the silicon atom of the organohydrodiene polysiloxane is not particularly limited, except that it is not an aryl group, and may be various organic groups; is preferably a methyl group.

Specifically, such organohydrodiene polysiloxanes include (CH:+)H5iO units, H5+0+
, s unit, (CH,)2SiO unit, (CH:l)
1sio. Examples include homopolymers or copolymers consisting of , , units, which may be linear, branched, or cyclic.

In addition, this organohydrodiene polysiloxane has 2
The viscosity at 5°C is 10 to 500 cp, especially 15 to 2
00 cp is preferred.

In the present invention, the amount of organohydrodiene polysiloxane as component (B) described above is desirably adjusted depending on the amount of alkenyl groups contained in the organopolysiloxane as component (A). From the viewpoint of film-forming ability and peeling performance, it is preferably in the range of 0.5 to 30 parts by weight, particularly 1 to 10 parts by weight, per 100 parts by weight of component (A).

C alcohol 4 Organopolysiloxane In the present invention, in addition to the above-mentioned components (A) and (B), the component (
An aryl group-containing organopolysiloxane is used as C). The combination of component (C) improves excellent releasability and residual adhesion.

This aryl group-containing organopolysiloxane has the above-mentioned formula (I), that is, R:+5iO(RzSiO)XSiRx CI
] (wherein R and χ are as described above).

Here, to explain the above-mentioned formula [I] in detail, the substituent R bonded to the silicon atom is a hydrogen atom; a vinyl group,
Indicates one selected from the group consisting of alkenyl groups such as allyl groups; alkyl groups such as methyl, ethyl, and propyl groups; and aryl groups such as phenyl and tolyl groups.

Also, 0.5 to 30 mol% of the total R group, preferably 1 to 2
0 mol% is an aryl group. The proportion of aryl groups is 0.
If the amount is less than 5 mol %, the easy release effect will be low, and if it exceeds 30 mol %, the effect will not improve and will not only remain constant, but will also have an adverse effect on the residual adhesiveness.

Further, among these plurality of R groups, at least one, preferably 1 to IO, and preferably 1 to 5 R groups is a hydrogen atom or an alkenyl group. Of course, it includes both hydrogen atoms and alkenyl groups. That is, the aryl group-containing organopolysiloxane of component (C) contains such a hydrogen atom and/or alkenyl group in its molecule, so that during the addition curing reaction of the components (A) and (B), The SiH group or alkenyl group is also the component (A
) or with the alkenyl group or SiH group in component (B), and this aryl group-containing organopolysiloxane is incorporated into the cured film. As a result, bleed-out of the aryl group-containing organopolysiloxane is effectively suppressed, and a decrease in residual adhesion rate is effectively avoided. Moreover, since the above-mentioned addition reaction further progresses due to aging of the silicone-coated evaporator, silicone migration properties are also improved. In the present invention, if the aryl group-containing organopolysiloxane molecule contains neither a hydrogen atom bonded to a silicon atom nor an alkenyl group, even if the light peeling force is sufficient, the residual The inconvenience of reduced adhesion cannot be avoided. Furthermore, if the content of such hydrogen atoms and alkenyl groups in the aryl group-containing organopolysiloxane is greater than the above-mentioned range, the light release effect may be unsatisfactory.

The bonding position of the hydrogen atom (SiH group) and the alkenyl group described above is arbitrary, but from the viewpoint of easy peeling effect, it is desirable that it be at the end of the molecular chain, especially only on one side of the end of the molecular chain.

Further, X in the above formula is preferably an integer such that the viscosity of the aryl group-containing organopolysiloxane at 25° C. is from 500,000 to 1,000,000 cp, particularly from 200 to 100,000 cp. If the viscosity of the aryl group-containing organopolysiloxane is less than 50 cp, the light release effect will be small, and if it is greater than 1 million cp, the light release effect during high-speed peeling will not tend to be obtained.

Specific examples of such aryl group-containing organopolysiloxanes are illustrated below.

CH.

CH3 C, H5 CH3 CH3 CH.

CH3 [However, in the formula, m and n have a viscosity of 50 cp at 25°C
~1 million cp, preferably further,
It is a value that satisfies the following formula. ] The blending amount of the above-mentioned aryl group-containing organopolysiloxane is preferably in the range of 0.3 to 20 parts by weight, particularly 0.5 to 10 parts by weight, per 100 parts by weight of the organopolysiloxane of component (A). .

If it is less than 0.3 parts by weight, the light release effect may not be sufficient, and if it exceeds 20 parts by weight, it may have an adverse effect on the residual adhesion rate and curability.

D Platinum Gold In the present invention, in order to effectively advance the addition curing reaction, a conventionally known platinum group metal catalyst as this type of addition reaction catalyst is used as component (D). Specific examples of such catalysts include platinum-based, palladium-based, and rhodium-based catalysts, with platinum-based catalysts being particularly preferred, such as chloroplatinic acid, alcoholic solutions of chloroplatinic acid, aldehyde solutions, and chloroplatinic acid. Examples include complexes with various olefins and vinyl siloxanes.

The amount of platinum group metal catalyst to be added may be a catalytic amount, but in order to obtain a good cured film and from an economical point of view, the amount of platinum group metal based on 100 parts by weight of component (A) should be 1.
The range is preferably 1,000 ppm to 1,000 ppm.

In addition to the above-mentioned components, other optional components may be added to the composition of the present invention, such as various organic nitrogen compounds, organic phosphorus compounds, acetylene, etc., for the purpose of suppressing the catalytic activity of platinum compounds. Activity-suppressing compounds such as compound, oxime compound, organic chloro compound, etc. may be added as necessary.

The silicone composition of the present invention is easily prepared by uniformly mixing the above-mentioned components.

Although there are no particular restrictions on the mixing method, it is preferable to uniformly mix components (A) to (C) in advance and then add component (D), a platinum group metal catalyst.

The silicone composition thus prepared is used as a release paper by applying it to a substrate such as paper or plastic film, and then heating and curing it in a conventional manner to form a cured coating.

(Effects of the Invention) The silicone composition of the present invention is extremely useful as a release paper, and the release paper formed using this composition can be easily peeled off at low and high speeds, and does not leave any residue. Provides a release film with little decrease in adhesion rate. Therefore, by using the composition of the present invention, it is possible to speed up the unwinding process in the production of adhesive paper, the scrap removal process in the production of adhesive labels, the label pasting process, etc., streamlining the process and improving workability. I can do it.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples below.

In addition, in the following examples, all parts are parts by weight, and the viscosity is a value at 25°C.

Moreover, the peeling force and residual adhesion rate of the silicone composition were measured by the following method.

<Peeling force> A predetermined amount of the silicone composition is applied to the surface of a thin film or sheet-like base material, and after heating in a hot air dryer at a predetermined temperature for a predetermined time to form a cured film, the surface of this cured film is Acrylic solvent-based adhesive Olipine BPS-512
7 (manufactured by Toyo Ink Manufacturing Co., Ltd.) or an acrylic emuldigon type adhesive Olivine BPW-3110H (manufactured by Toyo Ink Manufacturing Co., Ltd.) was applied and heat-treated at 100° C. for 3 minutes.

Next, a high-quality paper with a weight of 64 g/m" was attached to this treated surface, and after aging at 25°C for 20 hours under a load of 20 g/m2, the sample was cut into 5 cm width and tested using a tensile tester. Peeling speed 0.3 m/min at 180° angle, 6
The bonded paper was pulled at 0 m/min and the force (g) required to peel it off was measured.

<Residual adhesion rate> After forming a cured film of the silicone composition on the surface of the base material in the same manner as in the case of peeling force measurement, a polyester tape (trade name Lumirror 31B manufactured by Nitto Denko ■) was attached to the surface, and 20 g After heating and aging at 70°C for 20 hours under a load of /m2, the tape was removed and attached to a stainless steel plate.

Next, this tape was peeled off from the stainless steel plate at an angle of 180° at a peeling rate of 0.3 ta1 minute, and the force (g) required for peeling was measured. In addition, the force (g) required to peel off the untreated tape to which the silicone cured film was not attached from the stainless steel plate was measured, and the ratio of these values was calculated and expressed as a percentage.

[Example 1, Comparative Example 1.2] Component (A) was dimethylpolysiloxane 10 with a viscosity of 400 cp and whose molecular chain terminals were blocked with dimethylvinyl groups.
0 parts as component (B), 2.0 parts of methylhydrodiene polysiloxane with a viscosity of 20 cp and containing 20 mol% of dimethylsiloxane units and whose molecular chain ends are capped with trimethylsilyl groups, and as component (C) with dimethylvinyl terminals. Each is blocked with a silyl group and a trimethylsilyl group,
Viscosity 3, containing 5 mol% diphenylsiloxane units.
1.8 parts of 000 cp methylphenylpolysiloxane and 0.25 parts of 1-ethynyl-1-cyclohexanol.
A silicone composition (A) (Example 1) was prepared by mixing the mixture and stirring the mixture uniformly, and then adding a complex of platinum and vinyl siloxane in an amount of too ppm in terms of platinum.

Furthermore, the silicone composition was prepared in the same manner as above, except that methylphenylpolysiloxane having a viscosity of 3,000 cp and containing 5 mol% of diphenylsiloxane units and whose ends were capped with trimethylsilyl groups was used as component (C). A silicone composition (c) (comparative example 2) was prepared in the same manner as in example 1, except that component (b) (comparative example 1) was not added.

Next, the silicone compositions (a) to (c) were applied to polyethylene laminate paper at a coating amount of 0.8 g/rm2, and cured at 140°C for 30 minutes to determine the peeling force and residual The adhesion rate was measured.

The results are shown in Table 1.

Table 1 From the results in Table 1, when an aryl group-containing organopolysiloxane whose terminals are not capped with dimethylvinylsilyl groups is blended as component (C) (Comparative Example 1), the residual adhesion rate decreases, and the component When (C) is not added (Comparative Example 2)
requires a large peeling force, but it was confirmed that the silicone composition of the present invention (Example 1) can be easily peeled off at low and high speeds and provides a release film with little reduction in residual adhesion.

[Example 2, Comparative Examples 3 to 6] Component (A) was a rubbery polydimethylsiloxane whose molecular chain terminals were capped with dimethylvinyl groups and whose methylvinylsiloxane units were 1.5 mol% (dissolved at 30% in toluene). 100 parts, the viscosity is 5,000 cp)
20 whose terminal end was blocked with a trimethylsilyl group as B)
2.4 parts of cp methylhydrodiene polysiloxane,
Component (C) is 15 parts of methylphenylpolysiloxane whose end is capped with a trimethylsilyl group, has one methylhydrodienesiloxane unit in the molecule, and further contains 3 mol% of diphenylsiloxane units, and has a viscosity of 10°000 cρ. , 3 parts of a silicon compound having an acetylenically unsaturated group represented by the following formula % are mixed, and after uniformly dissolving using toluene so that the active ingredient is 30%, platinum and vinyl siloxane are added to this. A silicone composition (d) was prepared by adding the complex to 1100 pp in terms of platinum (Example 2)
.

Furthermore, as component (C), a methylphenylpolysiloxane having a viscosity of 10.000 cp containing 3 mol% of diphenylsiloxane at the 1m position, whose terminal end is capped with a trimethylsilyl group, and a methylhydrodiene siloxane unit whose end is capped with a trimethylsilyl group; It has one diphenylsiloxane unit in the molecule and contains 0.2 mol% and has a viscosity of 10
．． Methylphenylpolysiloxane of 0OOcp, end-capped with trimethylsilyl group, has one methylhydrodienesiloxane unit in the molecule, and further contains 40 mol% of diphenylsiloxane units, and has a viscosity of 10.0OO
Silicone compositions (e) and (
Prepare silicone composition '!) and (g) in the same manner as above except that component (C) is not added. #(H) was prepared (Comparative Examples 3 to 6).

Next, these silicone compositions (d) to (h) were applied to polyethylene laminate paper at a coating amount of 0.8 g/m2, and cured at 140°C for 30 minutes to determine their peeling strength and residual strength. The adhesion rate was measured.

The results are shown in Table 2.

From the results in Table 2, it can be seen that the terminal of component (C) is capped with a dimethylhydrodienesilyl group, and the terminal group is blocked by 0.5
It was found that the release paper prepared from the composition of the present invention containing ~30 mol % of organopolysiloxane was easy to peel when peeled at low and high speeds, and there was little decrease in residual adhesion.

Claims (2)

[Claims] (1) (A) An organopolymer having a viscosity of 50 centipoise or more at 25°C, containing no aryl group in its molecule, and having at least two alkenyl groups bonded to silicon atoms in each molecule. Siloxane, (B) an organohydrodiene polysiloxane that does not contain an aryl group in its molecule and has at least two hydrogen atoms bonded to silicon atoms in one molecule, (C) the following general formula, R_3SiO( R_2SiO)_xSiR_3, where R
represents one selected from the group consisting of a hydrogen atom, an alkenyl group, an alkyl group, and an aryl group, at least one of the plurality of R's is a hydrogen atom or an alkenyl group, and 0.5 to 30 of all R's an organopolysiloxane in which mol% is an aryl group, X is a positive integer, and has a viscosity of 50 to 1,000,000 centipoise at 25°C; (D) contains a platinum group metal catalyst; silicone composition. (2) A release paper characterized in that a cured coating film of the silicone composition according to claim (1) is formed on a base material made of paper or a plastic film.