JPS6118950B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a silicone pressure-sensitive adhesive composition, and more specifically, it is an object of the present invention to provide a composition that can be easily peeled off from release paper that is generally available on the market. Currently known silicone adhesives exhibit their performance as adhesives within a temperature range of -65°C.
It has a temperature range of 260°C, which is much wider than other organic adhesives, and there is almost no deterioration in electrical properties even in high-temperature, high-humidity environments. Despite its excellent adhesion to textiles, plastics, silicone rubber, silicone varnish cloth, and Teflon (trade name), it usually does not adhere to silicone-treated release paper. Currently, its use is limited due to the On the other hand, silicone release paper can be used for adhesives other than silicone rubber, such as natural rubber or acrylic rubber, but they are not as good as silicone rubber adhesives in terms of heat resistance, water resistance, or flame retardancy. It has the disadvantage of being inferior. The present invention aims to provide a new silicone pressure-sensitive adhesive composition that eliminates the conventional disadvantages as described above. [In the formula, R ¹ represents a hydrogen atom or a monovalent hydrocarbon group. a and b are each 0.5≦a≦
1.9, 0≦b≦0.7. However, a+b is 0.7≦
100 parts by weight of organopolysiloxane containing 0.5% by weight or more of hydroxyl and/or alkoxy groups, (b) 10 to 100 parts of unvulcanized acrylic rubber having a number average molecular weight of 50,000 to 3,000,000. 80 parts by weight and (c) General formula (R ² ) _c Si (OR ³ ) _4-c ...(ii) [In the formula, R ² is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, R ³ represents a hydrogen atom or an alkyl group. c is 0, 1, 2 or 3] or a partially hydrolyzed condensate thereof. The silicone adhesive consisting of the above-mentioned components (a) to (c) has the various properties of silicone itself, such as heat resistance, water resistance, electrical properties, and flame retardancy, and has excellent adhesion to various substrates. It has the advantage that it not only shows good properties but also can be easily peeled off from commercially available silicone release paper. Hereinafter, the silicone adhesive composition according to the present invention will be explained in detail. First, the organopolysiloxane as component (a) used in the present invention has the above-mentioned average composition formula:
A siloxane represented by (i) having a phenyl group directly bonded to a silicon atom in its molecule, which has adhesive properties to the pressure-sensitive adhesive obtained from the composition of the present invention.
It provides adhesiveness and anchoring properties. In addition, this component (a) also provides the adhesive with the heat resistance, water resistance, and electrical properties inherent to silicone. In the formula, R ¹ represents a hydrogen atom or a monovalent hydrocarbon group, and examples of the monovalent hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group, and an alkenyl group such as a vinyl group or an aryl group. Examples include bases. a, b and a+b are as described above. As mentioned above, it is essential that this (a) component contains a predetermined amount of phenyl group, but this phenyl group plays a role in increasing the compatibility with the (b) component, and commercially available silicone release paper Since it is treated with a release agent containing dimethylpolysiloxane or methylhydrodienepolysiloxane as a main component, it has the effect of minimizing the affinity with these release agents. However, this (a)
The content of phenyl group in the component is 1 silicon atom
The range is 0.5 to 1.9 pieces per piece. Furthermore, it is essential that the ratio of the total amount (a+b) of phenyl group (C ₆ H ₅ ) and hydrogen atom or monovalent hydrocarbon group (R ¹ ) per silicon atom is in the range of 0.7 to 1.9. However, if a+b is less than 0.7, the adhesive obtained from the composition of the present invention will not have sufficient adhesive strength and will become hard and brittle, making it difficult to use. If the adhesive exceeds this value, the cohesive force of the adhesive will be insufficient, and if an adhesive containing such siloxane (a + b of 1.9 or more) is applied to adhesive tapes, labels, etc., the adhesive will peel off. Furthermore, this component (a), siloxane, has a hydroxyl group and/or an alkoxy group in its molecule.
It is necessary to contain 0.5% by weight or more, but if it is less than 0.5% by weight, sufficient anchoring force and cohesive force cannot be obtained for the base material. This component (a) can be prepared by conventionally known methods such as phenyltrichlorosilane, diphenyldichlorosilane, phenyltrialkoxysilane, diphenyldialkoxysilane, diphenylsilanediol, or a mixture thereof. If necessary, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, methyldichlorosilane, trichlorosilane, vinylmethyldichlorosilane, vinyltrichlorosilane, or one of the alkoxysilanes equivalent to these.
It can be easily obtained by (co)hydrolyzing a species or a mixture of two or more species. Next, the unvulcanized acrylic rubber used in the present invention is essential for increasing the adhesive strength and cohesive force of the adhesive obtained from the composition of the present invention, and providing stiffness as an adhesive. It is said to be a component of This component (b) has a number average molecular weight of 50,000 to 300
However, if the number average molecular weight is less than 50,000, sufficient cohesive force cannot be imparted to the adhesive obtained from the composition containing it; This is because if it exceeds this, the compatibility with the component (a) becomes poor or the desired adhesive strength cannot be obtained. Such acrylic rubbers include copolymerized products of alkyl esters of acrylic acid or methacrylic acid and hydroxyalkyl acrylic esters, 2-chloroethyl vinyl ether, acrylonitrile, or acrylamide, and ethyl acrylate or butyl acrylate as main components. and 0.1 to 5 mol% of hydroxypropyl acrylate or hydroxyethyl acrylate, etc.
(preferably 0.5 to 2 mol%). In addition, in the present invention, for the purpose of improving the physical properties of acrylic rubber, acrylic rubber is copolymerized with a modifier such as butadiene, vinyl acetate, chloroprene, or isobutylene as a comonomer, and these groups are introduced into the main chain. Although they can be used, it is desirable that they contain 60 mol% or more of acrylic units. In addition, in the present invention, the number average molecular weight is 300
Even if the acrylic rubber has a molecular weight of more than 10,000 yen, molecular chains are cut by roll mastication or kneading with a kneader applying high shearing force, and as a result, the molecular weight falls within the above range. It can be used if it is like this. From the standpoint of achieving the above-mentioned objective, the amount of component (b) used must be in the range of 10 to 80 parts by weight per 100 parts by weight of component (a). Furthermore, the component (iii) used in the present invention is an organosilicon compound represented by the above general formula (ii) or a partially hydrolyzed condensate thereof, in which R ² is a hydrogen atom or a substituted or unsubstituted Represents a monovalent hydrocarbon group, including alkyl groups such as methyl, ethyl, propyl, or butyl, alkenyl groups such as vinyl or allyl, aryl groups such as phenyl, and alkaryl groups such as tolyl. , or groups in which the hydrogen atoms of these groups are partially substituted with organic groups such as halogen atoms, amino groups, epoxy groups, acyl groups, or mercapto groups. Further, R ³ represents a hydrogen atom or an alkyl group, and examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a 1-methoxyethyl group. c is as described above. Examples of such organic silicon compounds include those shown below. ( _C6H5 ) _2Si ( _OH ) ₂ , _C6H5 (CH3 _{) 2SiOH} , _{C6H5 ( CH3} )Si(OH) _{2 , C6H5} ( _{CH3 )} Si
(OH) ₂ , (CH ₃ ) ₂ Si(OCH ₃ ) ₂ , (C ₆ H ₅ ) ₂ Si(OCH ₃ ) ₂ , CH ₂ =CH−Si(OC ₂ H ₅ ) ₃ , C ₆ H ₅ ( _CH3 ）Si
( _OCH3 ) _{2 , C6H5} (H)Si( _OC2H5 ) ₂ , _CH2 =CH- _Si
(OCH ₂ CH ₂ OCH ₃ ) ₃ , NH ₂ CH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si(OCH ₃ ) ₃ , From the viewpoint of achieving the object of the present invention as described above, it is essential to use the component (c) in an amount of 1 to 60 parts by weight based on 100 parts by weight of the component (a). The composition of the present invention is achieved by uniformly mixing the above components (a) to (c). Specifically, components (a) and (b) are mixed in a common solvent, such as xylene. Or aromatic hydrocarbon solvents such as toluene,
A method is adopted in which the component (3) is dissolved in an ester solvent such as butyl acetate or isopropyl acetate, or a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone, and the component (iii) is mixed therein. In addition, if component (c) does not dissolve in the solvent mixture of components (a) and (b), and cloudiness or precipitation occurs, heat and stir the components (a) to (c). A condensation reaction may be carried out between the components, and water or alcohol produced by the condensation may be removed from the system. In carrying out the above condensation reaction, conventionally known condensation catalysts such as organic acid salts of metals such as zinc, titanium, tin or lead or amine compounds are used to shorten the time required for the reaction. There is no problem in using a small amount. However, if the condensation reaction is carried out more than necessary, the viscosity becomes high and coating work becomes poor, and the reactive polar groups such as alkoxy groups such as methoxy or ethoxy groups and hydroxyl groups are reduced, resulting in a The reaction may be stopped when the solution becomes clear, since this may cause disadvantages such as deterioration of the properties as a solvent. In addition, when preparing the composition of the present invention, as component (A), a+b is 0.7 to 1.2, and a is
Use 100 parts by weight of 0.9 to 1.2, and 1 part of component (C).
When ~10 parts by weight is used, it becomes solid and has poor adhesiveness at room temperature, but when heated to 80°C or higher (preferably 100°C or higher), it melts and becomes sticky and adhesive. Therefore, it can also be used as a hot melt adhesive. On the other hand, when component (a) having the same molecular structure as above is used and component (c) is used in an amount of 10 to 60 parts by weight, it is generally preferable to use it in a solution state. For example, 10,000 to 100,000 cS for a solution with an active ingredient concentration of 50%
(25°C) is dissolved in an organic solvent as mentioned above to adjust the viscosity to 1000-5000cS (25°C).
After uniformly applying it to various base materials used for regular adhesive tapes and labels, such as polyester film and paper, the solvent is removed by blowing hot air at room temperature or below 150°C, making it sticky even at room temperature. Adhesive tapes, labels, badges, etc. can be obtained. It is usually sufficient that the amount of the adhesive obtained by the present invention applied to the substrate is in the range of about 10 to 100 μm. The composition of the present invention may contain an inorganic filler having excellent heat resistance such as quartz powder, aluminum oxide, magnesium oxide, fumed silica, carbon, glass powder, calcium carbonate, or titanium oxide, if necessary. According to this, the heat resistance, thermal conductivity, or flame retardance of the adhesive obtained from the composition of the present invention can be further improved.
If too large amounts of these are used, the adhesion will drop significantly, so the amount used is desirably 20 parts by weight or less per 100 parts by weight of the total amount of components (a) to (c). The adhesive obtained from the composition of the present invention can be peeled off from the adherend to which it has been applied and reapplied to another adherend in the same way as ordinary adhesives, if the use temperature is 200°C or lower. Moreover, at a working temperature of 200 to 300°C, a crosslinking reaction progresses and a gelation phenomenon is observed, allowing it to be used as a strong permanent adhesive. Next, Examples and Comparative Examples of the present invention will be shown, and in each example, parts indicate parts by weight, and wt% indicates weight %. Example 1 Polysiloxane represented by the average composition formula (CH _{3 ) 0.32 (C 6 H 5 ) 0.88 SiO 1.4 and containing 3.1 wt % of} hydroxyl groups directly bonded to Si atoms and 2.6 wt% _of butoxy groups 100 parts, 30 parts of acrylic rubber (crude rubber) having a number average molecular weight of 150,000 and 2.5 mol% of hydroxypropyl acrylate as a functional group, uniformly dissolved in 300 parts of toluene, and NH ₂ CH ₂ CH ₂ NHCH ₂ CH ₂ CH _2Si
When 20 parts of (OCH ₃ ) ₃ (KBM-603 manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed and dissolved, an adhesive with a viscosity of 8,500 cS (25° C.) was obtained. Furthermore, 100 parts of toluene was added to adjust the viscosity to 3500cS (25°C), and then it was applied uniformly to a 19mm wide Teflon tape (trade name) using an applicator and heat treated at 120°C for 3 minutes to remove the solvent. When removed, the thickness of the adhesive layer was 30μ
m adhesive tape was obtained. When various physical properties of this adhesive tape were investigated, the following results were obtained. Adhesive strength (J.Dow ball tag NO) ...14 Adhesive strength (attached to stainless steel plate SUS27C.P280G,
180 peel force) ...950g/19mm width Cohesive force (displacement distance when a tape of 10mm width and 20mm length is applied to a stainless steel plate and pulled for 30 minutes with a force of 1Kg) ...0.35mm Also, commercially available A silicone release paper was attached, and then a 2 kg rubber roller was moved back and forth 10 times to apply pressure, and then this was left in a room at 40°C for one month. When the release paper was removed one month later, it was easily removed. When the adhesive strength and adhesion strength of this product were measured, the adhesive strength was 14, and the adhesive strength was 940 g/19 mm width, and it was confirmed that this product could be sufficiently put to practical use. Example 2 To 100 parts of polysiloxane having an average compositional formula (CH ₃ ) _0.13 (C ₆ H ₅ ) _1.1 SiO _1.38 and containing 2.1 _wt % of hydroxyl groups, a number average molecular weight _of 250,000 and hydroxypropyl as a functional group was added _. A mixture of 40 parts of acrylic rubber (raw rubber) containing 2.5 mol% of acrylate uniformly dissolved in 300 parts of toluene and CH ₂ =CHSi(OCH ₂ CH ₂ OCH ₃ ) ₃
(KBC1003 manufactured by Shin-Etsu Chemical Co., Ltd.) When 15 parts were added and uniformly dissolved, an adhesive with a viscosity of 13000cS (25°C) was obtained. Furthermore, 150 parts of butyl acetate was added to adjust the viscosity to 4300 cS (25°C), and then it was applied uniformly to a 19 mm wide Teflon tape and heat treated at 120°C for 3 minutes to remove the solvent. An adhesive tape with a thickness of 35 μm was obtained. The physical properties of the adhesive surface of this adhesive tape were as follows. Adhesive strength: 4 Adhesive strength: 870g/19mm width Cohesive strength: 0.15mm After applying commercially available silicone release paper to the adhesive side of this tape and applying pressure by moving a 2kg rubber roller back and forth 10 times, It was left at 40°C for one month. Even after one month, the release paper peeled off lightly, so I measured the adhesive strength and adhesive strength of the adhesive tape, and the adhesive strength was 4.
The weight was 880g/19mm width, and it was confirmed that this product could be put to practical use. Example 3 Average composition formula (CH _{3 ) 0.13 (} C _{6 H 5} ) _1.6 (H) _0.10
SiO _1.09 with 0.8wt% hydroxyl group and 2.0wt _% ethoxy group
% of polysiloxane, 50 parts of the acrylic rubber (raw rubber) used in Example 1 was added to 300 parts of butyl acetate.
and CH ₃ (C ₆ H ₅ ) Si
(OCH ₃ ) When 30 parts of ₂ were mixed and dissolved, the viscosity was
An adhesive of 9000 cS (25°C) was obtained. Furthermore, 150 parts of toluene was added to adjust the viscosity to 2500cS (25℃), and then it was applied uniformly to a 19mm wide glass cloth tape using an applicator, and when the solvent was removed by heat treatment at 130℃ for 3 minutes, it became sticky. An adhesive tape with an agent layer thickness of 25 μm was obtained. The physical properties of this tape were as follows. Adhesive strength…12 Adhesive strength…1100g/19mm width Cohesive strength…0.33mm Silicone release paper was pasted on the adhesive side of this tape and left at 40℃ for 2 months, then the release paper was peeled off. It was easily peeled off. After 2 months, the adhesive strength was 12, and the adhesive strength was 1,100 g/19 mm width. Example 4 Average composition formula (CH ₂ = CH _{) 0.22 (} C _{6 H 5 ) 1.2 SiO 1.29}
2.7wt% hydroxyl group, 3.3wt% methoxy group
% of polysiloxane, 60 parts of the acrylic rubber (crude rubber) used in Example 1 was uniformly dissolved in 300 parts of toluene, and (C ₆ H ₅ ) ₂ Si(OH) ₂
When 30 parts of the above were mixed, a cloudy white precipitate was produced. To this, tetrapropyl titanate was used as a condensation catalyst.
When the mixture was heated and a condensation reaction was carried out under reflux for 30 minutes, a homogeneous solution was obtained. When the solution was cooled, a solution of 20,000 cS (25°C) was obtained. Then add 200 parts of methyl isobutyl ketone to adjust the viscosity.
The temperature was adjusted to 5000 cS (25° C.), and 20 parts of titanium oxide powder was added and mixed by stirring until uniform. When applied uniformly to a 19 mm wide polyester film using an applicator and heat treated at 120°C for 5 minutes to remove the solvent, the adhesive layer thickness was 55 μm.
m adhesive tape was obtained. The physical properties of this tape were as follows. Adhesive strength: 30 Adhesive strength: 1,200g/19mm width Cohesive strength: 0.35mm Silicone release paper was applied to the adhesive layer of the above tape and left at 40℃ for 2 months, then the release paper was peeled off. As a result, it could be easily peeled off, and after two months, the adhesive strength was 30 and the adhesive strength was 1150 g/19 mm width. Example 5 To _{100 parts of polysiloxane having the average compositional formula (CH 3 ) 0.10 (C 6 H 5 ) 0.95 SiO 1.48 and containing 4.4 wt % hydroxyl groups} and 2.6 wt% methoxy groups, several Average molecular weight 800,000,
45 parts of acrylic rubber copolymerized with 1.0 mol% acrylonitrile as a functional group is mixed with methyl ethyl ketone.
Uniformly dissolved in a mixed solvent consisting of 150 parts and 150 parts of toluene

When 5 parts of [Formula] (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.) was added and completely dissolved, the viscosity of this product was 30,000 cS (25°C). Apply the mixture as is using an applicator.
When it was applied to a 19 mm Teflon tape and heat treated at 150°C for 10 minutes to completely remove the solvent, a tape with an adhesive layer thickness of 80 μm was obtained. This product had almost no tack at room temperature, and could be stored for a short time even with this tape layered over it. However, if it was kept for more than a week, blocking occurred during peeling, so a commercially available silicone release paper was bonded and wound into a roll. With this product, the silicone release paper could be easily peeled off even after two weeks had passed. After further heating at 150℃ for 3 minutes, the adhesive melted, so it was applied to a stainless steel plate as it was, and when it came to room temperature, the adhesive strength was measured, and it was 1500g/19mm width, indicating that it can be used as a hot melt type adhesive. I understood. Example 6 A polysiloxane having an average composition formula (C ₆ H ₅ ) _1.2 SiO _1.4 and a hydroxyl group content of _{4.7 wt} % has a number average molecular weight of 150,000 and hydroxypropyl acrylate as a functional group. A mixture of 40 parts of acrylic rubber (raw _rubber ) containing 2.5 mol% of acrylic rubber dissolved in 300 parts of toluene and 15 parts of _CH2 =CH-Si( _OC2H5 ) ₃ were uniformly dissolved. The viscosity of this product was 5300cS (25°C). After uniformly applying the mixture obtained above to a Teflon tape with a width of 19 mm, heat treatment was performed at 120°C for 3 minutes to obtain an adhesive tape with an adhesive layer thickness of 30 μm, and the adhesive surface of this tape The physical properties were as follows. Adhesive strength...4 Adhesive strength...830g/19mm width Cohesive strength...0.22mm Also, paste a commercially available silicone release paper on the adhesive surface, then apply pressure by moving a 2kg rubber roller back and forth 10 times. This was left in a room at 40°C for one month. When the release paper was peeled off after one month of peeling, it was possible to peel it off easily. When the adhesive strength and adhesion strength of this product were measured, the adhesive strength was 4 and the adhesive strength was 800 g/19 mm width, and it was confirmed that this product could be sufficiently put to practical use. Example 7 To 100 parts of polysiloxane having _an average compositional formula (CH ₃ ) _0.32 (C ₆ H ₅ ) _0.88 SiO _1.4 and containing 3.1 _wt % _of hydroxyl groups and 2.6 wt% of butoxy groups, several Average molecular weight 150,000, hydroxypropyl acrylate as a functional group
30 parts of acrylic rubber (raw rubber) containing 2.5 mol% dissolved in 300 parts of toluene and a partial hydrolyzate of phenyltrimethoxysilane (viscosity of 50% toluene solution 2.7 cS (25°C)), methoxy group content
27.6wt%, hydroxyl group content 4.7wt%, equivalent to diphenyldisiloxane) were mixed and dissolved.
An adhesive with a viscosity of 7700cS (25°C) was obtained. Furthermore, 100 parts of toluene was added to adjust the viscosity to 3300cS.
Apply this evenly to a 19mm wide Teflon tape,
When the solvent was removed by heat treatment at 120° C. for 3 minutes, an adhesive tape with an adhesive layer thickness of 30 μm was obtained. The physical properties of the adhesive surface of this adhesive tape were as follows. Adhesive strength…14 Adhesive strength…1050g/19mm width Cohesive strength…0.35mm In addition, commercially available silicone release paper was pasted on the adhesive surface, and a 2kg rubber roller was moved back and forth 10 times to apply pressure. This was left in a room at 40°C for one month. When I peeled off the release paper after one month,
It could be easily peeled off. When we measured the adhesive strength and adhesive strength of this item, the adhesive strength was 14,
The adhesive force was 940 g/19 mm width, and it was confirmed that this product could be used for practical purposes. Comparative Example 1 A commercially available silicone release paper was pasted on the adhesive side of a commercially available silicone adhesive tape (dimethylpolysiloxane type), and a load of 2 kg was applied and pressure was applied lightly back and forth twice with a roller, followed by being left at 40°C for 1 day. , the release paper was adhered. When I forcibly pressed the release paper, the adhesive side became brittle. Comparison ratio 2 300 parts of resin obtained by co-hydrolyzing 340 parts of ethyl polysilicate and 172 parts of trimethylchlorosilane
When a solution of 300 parts of dimethylpolysiloxane endblocked with hydroxyl groups (viscosity 3000000cS (25°C)) dissolved in 500 parts of toluene was added to the mixture and heated at 105°C for 10 hours, an adhesive solution of 200000cS (25°C) was obtained. Ta. Next, 1% benzoyl peroxide was added to the resin content to dissolve it, and toluene was added to adjust the viscosity to 10,000 cS (25°C). Then, it was applied to a Teflon tape with a width of 19 mm using an applicator. After heat treatment at 150℃ for 5 minutes,
An adhesive tape with an adhesive layer thickness of 60 μm was obtained. When we measured the physical properties of this product, the adhesive strength was 25, the adhesive strength was 850g/19mm width, and the cohesive strength was
It was 0.21mm. When a commercially available silicone release paper was attached to this adhesive surface and left for one day at 40°C, the paper adhered to each other and could not be peeled off.

Claims (1)

[Claims] 1 (a) Average compositional formula [In the formula, R ¹ represents a hydrogen atom or a monovalent hydrocarbon group. a and b are each 0.5≦a≦
1.9, 0≦b≦0.7. However, a+b is 0.7≦
100 parts by weight of organopolysiloxane containing 0.5% by weight or more of hydroxyl and/or alkoxy groups, (b) 10 to 100 parts of unvulcanized acrylic rubber having a number average molecular weight of 50,000 to 3,000,000. 80 parts by weight and (c) general formula (R ² ) _c Si(OR ³ ) _4-c [wherein, R ² is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, and R ³ is a hydrogen atom or Represents an alkyl group. c is 0, 1, 2 or 3] A silicone adhesive composition comprising 1 to 60 parts by weight of an organosilicon compound or a partially hydrolyzed condensate thereof.