JPH0684494B2 - Silicone pressure sensitive adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an addition reaction type silicone pressure-sensitive adhesive composition that can be cured to give a pressure-sensitive adhesive.

[Conventional technology]

Silicone pressure-sensitive adhesives have excellent characteristics such as adhesive strength, tackiness, tackiness, cohesive strength, etc. required as pressure-sensitive adhesives. In addition, silicone-specific heat resistance, cold resistance, electrical characteristics, etc. Because of its characteristics, it is widely used in electrical insulation tapes that require high reliability and various adhesive products that require heat resistance and cold resistance.

Generally, as the silicone pressure-sensitive adhesive composition, a composition composed of a mixture of a dimethylsiloxane polymer and a methylsiloxane resin and cured by an organic peroxide is used. Separately, a composition which is cured by an addition reaction between an alkenyl group-containing organopolysiloxane and a silicon atom-bonded hydrogen atom-containing organopolysiloxane has been proposed (see Japanese Patent Publication No. 54-37907).

[Problems to be solved by the invention] However, in order to use this as a pressure-sensitive adhesive,
It is necessary to heat and cure under high temperature conditions above ℃,
It could not be applied to heat-sensitive substrates. Also,
The latter can be cured at a lower temperature than the former, but it has a drawback that the adhesive strength is inferior to the former.

The present inventors have completed the present invention as a result of studying to solve the problems of the prior art.

An object of the present invention is to provide a pressure-sensitive adhesive composition that can be cured under relatively low temperature conditions, has excellent tack and cohesive strength, and can be a pressure-sensitive adhesive having particularly high adhesive strength. .

[Means for solving problems and their effects]

The above-mentioned purpose is (A) general formula (In the formula, R is a monovalent hydrocarbon group, R ¹ is an alkenyl group, and n is an integer.) 30 to 70 parts by weight of diorganopolysiloxane (B) R ² ₃ SiO _1/2 unit (In the formula, R ² is selected from an alkyl group, an alkenyl group and a hydroxyl group, and at least all R ² groups are
95 mol% is a methyl group. ) And SiO ₂ units, the molar ratio of which is in the range of (0.6: 1) to (0.9: 1) and the content of silicon atom-bonded hydroxyl groups is in the range of 0 to 1% by weight. To 30 parts by weight (C) Organopolysiloxane having at least two silicon atom-bonded hydrogen atoms in one molecule (A) To give 1 to 20 silicon atom-bonded hydrogen atoms per alkenyl group in the component Achieved by a solventless silicone pressure-sensitive adhesive composition comprising 0.1 to 1000 parts by weight of platinum metal per 1 million parts by weight of a sufficient amount and (D) platinum catalyst (A) to (C). To be done.

Explaining this, the component (A) is the main component of the pressure-sensitive adhesive composition of the present invention, and undergoes an addition reaction with the component (C) by the catalytic action of the component (D) to cure. Like this (A)
It is necessary that the component has an alkenyl group necessary for the addition reaction at the end of the molecular chain. In the above formula, R is an alkyl group such as methyl group, ethyl group, propyl group; vinyl group, allyl group,
An alkenyl group such as a propenyl group; a monovalent hydrocarbon group such as a phenyl group, and a methyl group is generally preferable. If heat resistance is required, a phenyl group may coexist with a methyl group. R ¹ is an alkenyl group such as a vinyl group, an allyl group or a propenyl group, preferably a lower alkenyl group.
The molecular weight of the component (A) is not particularly limited as long as the pressure-sensitive adhesive composition of the present invention does not impair processability in practical use. In particular, when the viscosity of the component (A) is 100,000 centipoise or less, a solventless pressure-sensitive adhesive composition having excellent workability can be obtained.

The component (B) is an organopolysiloxane component that imparts adhesive strength to the pressure-sensitive adhesive after curing, and R ^{2 in} the above formula is an alkyl group such as a methyl group, an ethyl group or a propyl group; a vinyl group,
Selected from an alkenyl group such as an allyl group and a hydroxyl group,
At least 95 mol% of all R ² groups are methyl groups. In the present invention, the content of alkenyl groups in all R ² groups is 0.
It is 5 mol% or less, preferably 0 mol%.

Then, the molar ratio of the R ² ₃ SiO _1/2 unit and the SiO ₂ unit is (0.6:
It must be in the range 1) to (0.9: 1). this is
If the R ² ₃ SiO _1/2 unit is less than 0.6, the adhesive strength will decrease to 0.9.
This is because the cohesive force is reduced when it exceeds. Methods for synthesizing such organopolysiloxanes are known.

The content of hydroxyl groups bonded to silicon atoms in the component (B) is 1% by weight or less, preferably 0.6% by weight or less, based on the total weight of the component (B).

This is because when the content of the hydroxyl group bonded to the silicon atom exceeds 1% by weight, high adhesive strength cannot be obtained. In the present invention, the organopolysiloxane having such a hydroxyl group content of 1% by weight or less is, for example, a resin-like organopolysiloxane obtained by a conventionally known synthesis method (for example, US Pat. No. 2,676,182).
(See Japanese Patent Laid-Open Publication), the hydroxyl group remaining therein is subjected to silylation treatment with a silylating agent typified by hexamethylsilazane to easily produce.

The component (C) is an organopolysiloxane that acts as a cross-linking agent for the component (A), and the silicon atom-bonded hydrogen atom in this component undergoes an addition reaction with the alkenyl group in the component (A) due to the catalytic action of the component (D). It cures. The component (C) is such that per alkenyl group in the component (A),
It suffices if the amount is sufficient to give 1 to 40 silicon atom-bonded hydrogen atoms. This is because if the number is less than 1 or more than 40, a sufficient cohesive force cannot be obtained. The molecular structure of the component (C) may be any form such as chain, net, or ring.

The component (D) is a platinum-based catalyst that promotes the addition reaction between the component (A) and the component (C). Specific examples of these are:
Examples thereof include chloroplatinic acid, a complex of chloroplatinic acid and an olefin, a complex of chloroplatinic acid and vinylsiloxane, or a substance in which platinum is supported on a fine powder carrier such as alumina. The amount of the component (D) added is from the components (A) to (C).
0.1 to 0.1% by weight of platinum metal based on the total amount of 1 million parts by weight
It is 1000 parts by weight, preferably 1 to 300 parts by weight. This is because if the amount is less than 0.1 parts by weight, the crosslinking reaction tends to be insufficient and the cohesive force tends to decrease, and if it exceeds 1000 parts by weight, the pot life becomes short and the cost becomes high, which is disadvantageous.

In the present invention, conventionally known addition reaction inhibitors may be added and blended in addition to the components (A) to (D). Specific examples of these include 3-methyl-1 butyne-
Acetylene alcohols such as 3-ol, 3.5 dimethyl-1-hexyn-3-ol, 3-methyl-1-penten-3-ol, phenylbutynol and 3-methyl-
3-penten-1-yne, 3.5-dimethyl-3-hexene-1-yne and the like can be mentioned.

In addition, it is possible to add minor amounts of additional ingredients to the compositions of the present invention. Such additional ingredients include various antioxidants, pigments, stabilizers, and fillers. In addition, as a base material for producing an adhesive product using the pressure-sensitive adhesive composition of the present invention, plastic films such as polyester, Teflon, and polyimide; paper such as Japanese paper and synthetic paper; cloth, glass wool, metal foil, and the like. The same material can be used.

〔Example〕

Next, the present invention will be described with reference to examples. The middle part of an Example shows a weight part and% shows weight%. Each property shown in the examples was measured by the following method.

○ Measurement method of adhesive strength A pressure-sensitive adhesive tape obtained by applying a silicone pressure-sensitive adhesive composition on a substrate to a predetermined thickness and then heat-curing the stainless steel plate (SUS304) whose surface has been polished with No. 280 water resistant abrasive paper. Use a 2 kg weight rubber roller to attach to. After standing at room temperature for 1 hour,
Tensile tester [Tensilon: Toyo Baldwin Co., Ltd.
The adhesive strength at the time of peeling was measured at a speed of 0.3 m / min, and was displayed in units of g / 2.5 cm.

○ Measurement method of cohesive force An adhesive tape made by the same method as the above-mentioned measurement method of adhesive force was applied to a stainless steel plate (SUS
304), and the area of 20 mm in length and 10 mm in width is attached by using a 2 kg weight rubber roller. A load of 500 g was applied to the lower end of this adhesive tape, and the displacement distance after hanging for 2 hours in an oven at 100 ° C. was measured with a reading microscope and displayed in mm.

○ Ball tack measurement method Adhesive tape made by the same method as the adhesive strength measurement is attached with the adhesive side up on a ball tack tester (manufactured by Tester Sangyo Co., Ltd.) with an inclination angle of 30 °. Rolling steel balls of various sizes with a 10 cm long runway, the diameter of the largest steel ball stopped on a 10 cm long sticky surface was shown in 1/32 inch increments.

For example, label 10 indicates that the 10/32 inch diameter steel ball was the largest steel ball that could have stopped on this adhesive surface. The measurement was performed at room temperature.

Example 1 (CH ₃ ) ₃ consisting of SiO _1/2 units and SiO ₂ units, the molar ratio of which is 0.
Methylpolysiloxane with a hydroxyl content of 0.5%, which is 7: 1.0, 50 parts, both ends with a viscosity of 40,000 centipoise, dimethylvinylsiloxy group blocked dimethylpolysiloxane (vinyl content 0.08%), 50 parts, both ends with a viscosity of 10 centipoise. Trimethylsiloxy group-blocked dimethylsiloxane-methylhydrogensiloxane copolymer (molar ratio of silicon atom-bonded hydrogen atoms to silicon atom-bonded methyl groups 1: 3) 0.4 parts and 3.5
0.2 parts of dimethyl-3-hexen-1-yne were mixed. In this mixture, the molar ratio of silicon-bonded atoms to vinyl groups was 2.2. Then, a vinylsiloxane complex of chloroplatinic acid was added to this so that the amount of platinum was 100 ppm with respect to the total amount of the polysiloxane to obtain a solventless pressure-sensitive adhesive composition. The methyl polysiloxane having a hydroxyl group content of 0.5% had a hydroxyl group content of 1.8% synthesized based on the method described in US Pat. No. 2,676,182.
Synthesized by adding 20 g of xylene and 7 g of hexamethylsilazane to 44 g of the methylpolysiloxane and being stirred under heating. This was applied to a 50-micron aluminum foil so as to have a thickness of 50 micron and cured at 100 ° C. for 3 minutes. The characteristics of the obtained aluminum-based pressure-sensitive adhesive tape were evaluated and the results shown in Table 1 were obtained.

Also, this solventless pressure-sensitive adhesive composition was enclosed in a 100 cc aluminum container and stored at room temperature for 6 months, and its storage stability was examined. There was no change in the container. For comparison, a pressure-sensitive adhesive composition having the same composition as above except that methylpolysiloxane having a hydroxyl group content of 0.5% was used in place of methylpolysiloxane having a hydroxyl group content of 0.5%, was obtained. The results of evaluation of this composition by the same method as described above are also shown in Table 1.

Further, this solventless pressure-sensitive adhesive composition was prepared in the same manner as described above.
It was sealed in a 0 cc aluminum container and stored at room temperature for 6 months. When its storage stability was examined, hydrogen gas was observed to be generated, and the aluminum container expanded.

EFFECTS OF THE INVENTION The silicone pressure-sensitive adhesive composition of the present invention comprises (A) a diorganopolysiloxane (B) R ² ₃ SiO _1/2 unit and a SiO ₂ unit having lower alkenyl groups at both ends of the molecular chain. From organopolysiloxane having a silicon atom-bonded hydrogen group content of 1% by weight or less, (C) an organopolysiloxane having at least two silicon atom-bonded hydrogen atoms in one molecule, and (D) a platinum-based catalyst Therefore, it has a feature that it can be cured under a relatively low temperature condition, has excellent tack and cohesive force, and can be a pressure-sensitive adhesive having particularly high adhesive force.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C09J 183: 04 183: 05) (C09J 183/07 183: 06 183: 05)

Claims (1)

[Claims] 1. A general formula (A) (In the formula, R is a monovalent hydrocarbon group, R ¹ is a lower alkenyl group, and n is an integer.) 30 to 70 parts by weight of diorganopolysiloxane (B) R ² ₃ SiO _1/2 units (in the formula, R ² is selected from alkyl group, alkenyl group and a hydroxyl group, at least of all the R ² groups
95 mol% is a methyl group. ) And SiO ₂ units, the molar ratio of which is in the range of (0.6: 1) to (0.9: 1), and the content of silicon atom-bonded hydroxyl groups is in the range of 0 to 1% by weight.
Organopolysiloxane 70 to 30 parts by weight (C) Organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in one molecule (1) to 40 silicon atoms per alkenyl group in component (A) Solventless silicone pressure-sensitive, consisting of 0.1 to 1000 parts by weight of platinum metal per 1 million parts by weight of the total amount of (D) platinum-based catalyst (A) to (C) components, sufficient to provide bonded hydrogen atoms. Adhesive composition.