JP5080224B2 - Solvent resistant silicone rubber composition - Google Patents

Description

  The present invention relates to a solvent-resistant silicone rubber composition that is cured by an addition reaction of polyorganosiloxane, and a solvent-resistant silicone rubber product that includes a cured product of the composition.

  Silicone rubber is known as a material excellent in heat resistance, cold resistance, weather resistance, and electrical insulation, and is used in parts such as O-rings, packings, and gaskets in various industrial fields. However, silicone rubber is easily expanded when immersed in a solvent and has poor solvent resistance, so its use has been limited. In particular, in recent years, engine oil for automobiles has been made to have a low viscosity so that it can be used even in cold regions. For this reason, the use of silicone rubber in the portion in contact with the engine oil has made it easier to expand, which has been a major obstacle to the use of silicone rubber in the automotive industry.

  In order to overcome the above drawbacks, it has been proposed to introduce a perfluoroalkyl-containing group into a silicone rubber to obtain a fluorinated silicone rubber (see, for example, Patent Documents 1 and 2). However, although resistance to nonpolar solvents and engine oil can be obtained by fluorination, a new problem arises that polar solvents such as ketones and lower alcohols are likely to expand. Further, the fluorinated silicone rubber is inferior in workability, and from the viewpoint of the environment, it is not preferable to use a halogen such as fluorine.

  On the other hand, the use of porous silica has been proposed as an attempt to improve the solvent resistance of silicone rubber without fluorination (see, for example, Patent Document 3). However, a sufficient improvement effect has not been obtained.

JP-A-63-205359 JP-A-5-186700 Japanese Patent Laid-Open No. 7-3161

  An object of the present invention is to provide a solvent-resistant silicone rubber composition that forms a cured product having good solvent resistance by heat curing. A further object of the present invention is to provide a solvent resistant silicone rubber product comprising a cured product of such a composition. In the present specification, the solvent resistance refers to a property that hardly expands when it comes into contact with a fuel oil such as a polar solvent, a nonpolar solvent, and engine oil.

  As a result of repeated studies to solve the above-mentioned problems, the present inventors have determined that the average value of the number of siloxane units of the linear polyorganosiloxane of the base polymer is within a specific range, and has a specific average particle diameter and aspect ratio. The present inventors have found that the problem can be solved by a silicone rubber composition using a mica powder having a ratio in combination, and have completed the present invention. In the silicone rubber composition of the present invention, by setting the average value of the number of siloxane units in the base polymer within a specific range, the average length between the crosslinking points of the cured product can be reduced. The apparent crosslink density of the cured product can be increased by blending mica having a layered structure. Together, these are considered to prevent solvent penetration into the cured product of the silicone rubber composition of the present invention and to exhibit solvent resistance.

That is, the present invention provides (A) Formula (I):

(Where
R is independently R ¹ or R ² , of which at least two are R ¹ ,
R ¹ is independently a C ₂ -C ₆ alkenyl group,
R ² is independently a C ₁ -C ₆ alkyl group or a phenyl group,
n is an average value of 10 to 2000) 100 parts by weight of a linear polyorganosiloxane represented by:
(B) Polyorganohydrogensiloxane having more than two hydrogen atoms bonded to silicon atoms in the molecule The number of hydrogen atoms bonded to silicon atoms for one alkenyl group present in (A) is 0.00. An amount of 5 to 10.0;
(C) Platinum group metal compound An amount containing 0.1 to 1,000 ppm by weight of platinum group metal atom relative to the amount of (A); and (D) An average particle diameter of 1 to 100 μm and an aspect ratio The present invention relates to a solvent-resistant silicone rubber composition containing 20 to 200 parts by weight of mica powder, which is 10 to 500, and relates to a solvent-resistant silicone rubber product made of a cured product of the composition.

  The silicone rubber composition of the present invention can be cured by heating to obtain a cured product having good solvent resistance. The silicone rubber product comprising the cured product of the silicone rubber composition of the present invention has excellent solvent resistance and can be expected to have the inherent heat resistance, cold resistance, weather resistance, and electrical insulation properties of the silicone rubber. Is expensive. In particular, since it does not easily expand even when it comes into contact with fuel oil such as engine oil, it can be suitably used for parts such as automobiles, vehicles, ships, airplanes and chemical plants.

  The component (A) used in the present invention has the formula (I):

(Where
R is independently R ¹ or R ² , of which at least two are R ¹ ,
R ¹ is independently a C ₂ -C ₆ alkenyl group,
R ² is independently a C ₁ -C ₆ alkyl group or a phenyl group,
n is an average value of 10 to 2000).

This component (A) is a component that becomes a base polymer in the solvent-resistant silicone rubber composition of the present invention, and is formed into a network by an addition reaction between R ¹ in the formula (I) and a hydrosilyl group in the component (B). A structure can be formed to form a cured product. By setting the average value n of the number of siloxane units of the component (A) to 10 to 2000, the average length between crosslinking points can be reduced. n is more preferably 20 to 1500, and still more preferably 30 to 1200.

In the formula (I), R ¹ is a C ₂ -C ₆ alkenyl group, which may be branched or linear, such as vinyl, allyl, 3-butenyl, 5-hexenyl, etc. Is exemplified. A vinyl group is most preferred because it is easy to synthesize and does not impair the fluidity of the composition or the heat resistance of the cured product. There are at least two R ^{1 s} in formula (I). At this time, R ¹ may be present in any siloxane unit in the molecule, but in order to obtain good reactivity, at least a part of R ¹ is preferably present at the molecular end, and at each end, More preferably, there are two R ¹ , one by one.

In the formula (I), R ² is a C ₁ -C ₆ alkyl group or a phenyl group. The C ₁ -C ₆ alkyl group may be branched or linear, and examples thereof include methyl, ethyl, propyl, etc., which are easy to synthesize and handle, and have thermal and mechanical properties. A methyl group is particularly preferred because it provides an excellent cured product.

From the viewpoint of improving solvent resistance, the component (A) in R ² is preferably 10 to 50 mol%, more preferably 30 to 50 mol% of the phenyl group.

The component (A) preferably has a viscosity at 23 ° C. of 0.01 to 500 Pa · s. When the viscosity is in this range, the composition has good fluidity and exhibits excellent workability, while giving a cured product having excellent mechanical strength and moderate elasticity and hardness. The viscosity can be adjusted by varying the mean value n and the type of R ² of the number of siloxane units. Generally, the larger n, the higher the viscosity, and the more phenyl groups introduced into R ² , the higher the viscosity. (A) The viscosity of a component becomes like this. More preferably, it is 0.05-100 Pa.s, More preferably, it is 0.1-20 Pa.s.

In the polyorganohydrogensiloxane of the component (B) used in the present invention, the hydrosilyl group contained in the molecule undergoes an addition reaction with R ¹ in the component (A), thereby cross-linking the component (A). It functions as an agent. Such a component (B) functioning as a crosslinking agent has more than two hydrogen atoms bonded to silicon atoms involved in the addition reaction in order to reticulate the cured product, preferably Have 3 or more.

The component (B) is typically represented by the general formula (II):
(R ³ ) _c H _d SiO _{(4-cd) / 2} (II)
(Where
R ³ represents an unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated carbon-carbon bond;
c is an integer from 0 to 2;
d is 1 or 2, provided that c + d is an integer of 1 to 3)
In the molecule, the number of units is more than 2, preferably 3 or more.

Examples of the organic group bonded to the silicon atom of R ³ and the other siloxane unit of component (B) are the same as those of R ^{2 in} component (A) described above, and among these, from the viewpoint of easy synthesis The methyl group is most preferred. Further, d is preferably 1 because synthesis is easy.

  The siloxane skeleton in the component (B) may be linear, branched or cyclic. Moreover, you may use these mixtures.

  The degree of polymerization of the component (B) is not particularly limited, but a polyorganohydrogensiloxane in which two or more hydrogen atoms are bonded to the same silicon atom is difficult to synthesize, and therefore preferably comprises three or more siloxane units. The number of siloxane units is more preferably 6 to 200, and particularly preferably 10 to 150, since it does not volatilize even when heated to the curing temperature, and is excellent in fluidity and easily mixed with the component (A).

The blending amount of the component (B) is a ratio of hydrogen atoms bonded to silicon atoms in the component (B) to R ¹ groups in the component (A) because a cured product having excellent mechanical properties can be obtained ( H / Vi) is such an amount that it is 0.5 to 10.0, preferably 1.0 to 5.0. When H / Vi is less than 0.5, the mechanical strength of the cured product is insufficient, and when it exceeds 10.0, the cured product tends to foam and the heat resistance of the cured product is significantly deteriorated.

The platinum group metal compound of component (C) used in the present invention is a catalyst for promoting the addition reaction between R ^{1 in} component (A) and the hydrosilyl group in component (B). As the platinum group metal compound, a compound of a platinum group metal atom such as platinum, rhodium, palladium is used, and chloroplatinic acid, a reaction product of chloroplatinic acid and an alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, Examples include platinum compounds such as platinum-ketone complexes and platinum-phosphine complexes; rhodium compounds such as rhodium-phosphine complexes and rhodium-sulfide complexes; and palladium compounds such as palladium-phosphine complexes.

  Of these, the reaction product of chloroplatinic acid and alcohol and a platinum-vinylsiloxane complex are preferred because of their good catalytic activity. When it is necessary to cure in a short time and develop adhesiveness, platinum- 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex and platinum-1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane are preferred. However, the necessary curing speed varies depending on the shape of the site where the cured product is provided and the required working time, and therefore can be arbitrarily selected depending on the combination of the component (C) and the curing retarder.

  (C) Since the compounding quantity of a component can obtain the outstanding hardening rate, it is 0.1-1,000 weight normally in conversion of a platinum group metal atom with respect to the total amount of (A) component and (B) component. ppm, preferably 0.5 to 200 ppm by weight. If it is less than 0.1 ppm by weight, the curing rate is slow, and even if it exceeds 1,000 ppm by weight, an increase in the curing rate commensurate with it cannot be obtained.

  (D) component used by this invention is a component which improves the solvent resistance of the hardened | cured material of the silicone rubber composition of this invention combined with (A) component. The component (D) has an average particle size of 1 to 100 μm and an aspect ratio of 10 to 500 from the viewpoint of improving solvent resistance. From the viewpoint of workability, the average particle diameter is preferably from 1 to 60 μm, and from the viewpoint of suppression of swelling to a solvent and workability, the aspect ratio is preferably from 20 to 250. Mica is generally a flat powder. Here, the average particle size of mica powder refers to the average value of the maximum diameter of the flat surface, and the aspect ratio refers to the value of the ratio of the long diameter and thickness of mica powder. Examples of the component (D) include natural mica such as muscovite, phlogopite, biotite, and synthetic mica. Mica is preferred because it has few impurities and gives excellent mechanical properties to the rubber-like elastic body as a cured product.

  (D) The compounding quantity of component is 20-200 weight part with respect to 100 weight part of (A) component from the point which provides sufficient solvent resistance and appropriate hardness to hardened | cured material, and 40-200 weight Part is preferred.

  If necessary, the silicone rubber composition of the present invention can be blended with an adhesion-imparting agent as long as the catalytic ability of the component (C) is not impaired. Examples of the adhesion-imparting agent include 3-glycidoxypropyl group-containing alkoxy such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropyl (methyl) dimethoxysilane. Silanes; 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl (methyl) dimethoxysilane Such 2- (3,4-epoxycyclohexyl) ethyl group-containing alkoxysilanes; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, methylvinyldimethoxysilane, allyltrimethoxysilane, allyltri Ethoxy Alkenylalkoxysilanes such as methyl and allyldimethoxysilane; 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-acryloxypropyl (methyl) dimethoxysilane, 3-methacryloxypropyltrimethoxy (Meth) acryloxypropylalkoxysilanes such as silane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyl (methyl) dimethoxysilane; hydrogen atoms bonded to silicon atoms and the following general bonds bonded to silicon atoms Formula (III):

(Wherein Q ¹ represents a linear or branched alkylene group forming a carbon chain having two or more carbon atoms between a silicon atom and an ester bond; Q ² represents an oxygen atom and a side. Represents a linear or branched alkylene group which forms a carbon chain having 3 or more carbon atoms between silicon atoms in the chain; R ⁴ represents an unsubstituted or substituted alkyl group having 1 to 6 carbon atoms; An aluminum silicon alkoxide such as aluminum triethoxide, aluminum tripropoxide, aluminum tributoxide; titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, Titanium alkoxides such as titanium tetrabutoxide, titanium tetraisobutoxide, titanium tetraisopropenyl oxide; Tetra isopropoxide, zirconium alkoxides such as zirconium tetrabutoxide; diallyl maleate, polar group-containing organic compounds such as triallyl isocyanate, and the like are exemplified.

In the side chain represented by the above general formula (III), Q ¹ is exemplified by an alkylene group such as ethylene, trimethylene, 2-methylethylene, tetramethylene, and the like. -A methylethylene group is preferred. Examples of Q ² include an alkylene group such as trimethylene, 2-methyltrimethylene, and tetramethylene, and a trimethylene group is preferable because synthesis and handling are easy. Examples of R ⁴ include alkyl groups such as methyl, ethyl, propyl, isopropyl, and butyl; and alkyl groups substituted with alkoxy such as 2-methoxyethyl, and alcohols that give good adhesion and are generated by hydrolysis Are easy to volatilize, methyl group and ethyl group are preferable, and methyl group is particularly preferable. As an organosilicon compound having such a side chain, formula (IV):

The cyclic siloxane compound shown by these is illustrated. The compounding amount of the adhesion-imparting agent varies depending on the kind of the adhesion-imparting agent and the substrate, but is usually in the range of 0.5 to 20 parts by weight with respect to 100 parts by weight of the component (A), and particularly the adhesiveness. From the viewpoint, 1 to 20 parts by weight is preferable, and 2 to 15 parts by weight is more preferable.

  In order to improve the storage stability and workability of the silicone rubber composition of the present invention, a curing inhibitor can be blended. The diallyl maleate is effective not only as an adhesion-imparting agent but also as a curing inhibitor. In addition, as the curing inhibitor, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynyl- Acetylene alcohols such as 1-cyclohexane-1-ol are exemplified.

The silicone rubber composition of the present invention is cured to form a cured product excellent in solvent resistance, but gives appropriate fluidity at the stage before curing, and the cured product is required depending on its use. In order to impart high mechanical strength, an inorganic filler can be added in addition to the component (D). Examples of the inorganic filler include reinforcing fillers having an average particle size of less than 0.1 μm and a specific surface area of 30 mm ² / g or more; and non-reinforcing fillers having an average particle size of 0.1 to 50 μm. Examples of reinforcing fillers include dry silica such as fumed silica and arc silica; and wet silica such as precipitated silica. These may be used as they are, and hydrophobic such as hexamethyldisilazane. You may use it after surface-treating with an agent. Non-reinforcing fillers include diatomaceous earth, ground quartz, fused quartz, titanium oxide, aluminum oxide, zinc oxide, aluminosilicate, calcium carbonate, organic acid surface treated calcium carbonate, magnesium carbonate, zinc carbonate, calcium silicate, Examples include talc and ferric oxide, which are selected according to the extrusion workability and the physical properties required for the cured product. Further, a conductive filler such as carbon black may be blended depending on the purpose.

  Further, according to the purpose, the silicone rubber composition of the present invention includes a pigment, a thixotropy imparting agent, a viscosity modifier for improving extrusion workability, an ultraviolet ray inhibitor, a fungicide, a heat resistance improver, a flame retardant. Various additives such as an agent may be added. In some cases, it may be dissolved or dispersed in an organic solvent such as toluene or xylene.

  The silicone rubber composition of the present invention is prepared by uniformly kneading the components (A) to (D) and other components blended as necessary with a mixing means such as a universal kneader or a kneader. Can do. Moreover, in order to stably store for a long period of time, two pre-blends are appropriately prepared and stored so that the (B) component and the (C) component are included in separate pre-blends, Immediately before use, the silicone rubber composition may be prepared by mixing uniformly by a mixing means such as a mixing head of a quantitative mixer, and defoamed under reduced pressure for use.

  The silicone rubber composition of the present invention can be cured by heating to obtain a cured product that is a rubber-like elastic body. The formation method of hardened | cured material is not specifically limited, For example, after inject | pouring the silicone rubber composition of this invention in a suitable type | mold, it can be heat-hardened and hardened | cured material can be formed. Alternatively, the silicone rubber composition of the present invention may be applied on an appropriate substrate and cured by heating to form a cured product. The curing conditions of the silicone rubber composition of the present invention can be arbitrarily set at a temperature between room temperature and 250 ° C. depending mainly on the type and amount of the component (C) and reaction inhibitor. The heating time is preferably 120 minutes or less, more preferably 60 minutes or less, and even more preferably 30 minutes or less. However, the curing conditions can be appropriately adjusted depending on the size of the member and the capacity of the heating furnace.

  The silicone rubber product comprising the cured product of the silicone rubber composition of the present invention has excellent solvent resistance and can be expected to have the inherent heat resistance, cold resistance, weather resistance, and electrical insulation properties of the silicone rubber. Is expensive. In particular, since it does not easily expand even when it comes into contact with fuel oil such as engine oil, it can be suitably used for parts such as automobiles, vehicles, ships, airplanes and chemical plants. Specific examples include application to sealing materials such as O-rings, packings, gaskets, internal materials for oil tanks, coating materials for electric / electronic substrates, and potting materials for electronic components.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In these examples, parts indicate parts by weight, and the viscosity indicates the viscosity at 23 ° C. The present invention is not limited by these examples.

In Examples and Comparative Examples, the following polysiloxanes were used as the components (A) and (B). Hereinafter, siloxane units are indicated by the following symbols. In the unit formula, the intermediate siloxane unit simply indicates the number of units. When a plurality of types of intermediate siloxane units are included, the intermediate siloxane units are randomly arranged.
^MH unit: (CH ₃ ) ₂ HSiO _1/2 −
M ^V _{unit: (CH 3) 2 (CH} 2 = CH) SiO 1/2 -
D unit: - (CH _{3) 2} SiO-
D ^ff _{Unit: - (C 6 H 5)} 2 SiO-
Q unit: SiO _4/2 (tetrafunctional)
A-1: both terminals blocked with M ^V unit, becomes the intermediate unit from D units, linear polymethylvinylsiloxane having a viscosity at 23 ° C. is at 3 Pa · s (mean 550 number siloxane units);
A-2: both terminals blocked with ^{M V} unit, consists 60 mol% intermediate units D units and ^{D ff} unit 40 mol%, the linear polymethyl vinyl siloxanes (siloxane units viscosity is 3 Pa · s Average value 30);
B-1: Branched polymethylhydrogensiloxane represented by the unit formula ^MH ₈ Q ₄

In Examples and Comparative Examples, the following platinum complex was used as the component (C).
C-1: Chloroplatinic acid-vinyltetramer complex (2% by weight in terms of platinum atom).

The following fillers were used in Examples and Comparative Examples.
D-1: muscovite powder having an average particle diameter of 5 μm and an aspect ratio of 65 D-2: muscovite powder having an average particle diameter of 22 μm and an aspect ratio of 70 D-3: muscovite powder having an average particle diameter of 50 μm and an aspect ratio of 80 D- 4: Average particle size of 2 μm, amorphous quartz powder

The following was used as a curing inhibitor.
E-1: 1-ethynyl-1-cyclohexanol

Examples 1 to 6 and Comparative Example 1
(Preparation of Preliminary Formula I)
In a container equipped with a stirrer, half of the amount of A-1 to A-2 shown in Table 1 and half of the amount of D-1 to D-4 shown in Table 1 are blended, and then shown in Table 1. Premix I was prepared by adding all of C-1 and E-1 and mixing until uniform.

(Preparation II preparation)
In the same apparatus, mix the remaining amount of A-1 to A-2, the total amount of B-1 shown in Table 1, and the remaining amount of D-1 to D-4, and mix until uniform. Preformulation II was prepared.

(Preparation of composition and production of silicone rubber sheet)
Preliminary formulation I and preliminary formulation II are charged in two containers of a quantitative mixer, respectively, and equal amounts of both preliminary formulations are supplied to the mixing head, mixed uniformly, and degassed under reduced pressure. Thus, a silicone rubber composition was prepared. Next, the silicone rubber composition was poured into a stainless steel mold having a polytetrafluoroethylene treatment on the surface and cured by heating at 150 ° C. for 30 minutes to obtain a silicone rubber sheet having a thickness of 1.0 mm. Produced.

  The silicone rubber sheets (thickness: 1.0 mm) of Examples 1 and 2 and Comparative Example 1 were punched out with a No. 2 dumbbell according to JISK6249 to prepare each test piece, and then xylene, n-hexane, 2 -Soaked in propanol or acetone. Each test piece was taken out after 72 hours, and the volume change rate before and after immersion was measured. The measurement results are shown in Table 1. Moreover, about the comparative example 1 and Example 2 and 5, the photograph before and behind immersion in xylene and n-hexane is shown.

As Table 1 shows, Examples 1-6 had a small volume change rate compared with the comparative example 1, and showed the outstanding solvent resistance. From comparison of Examples 1-3 with Examples 4-6, when using the same type of mica is that by using a base polymer phenyl group is introduced into R ^2, the effect of suppressing the volume change rate It was found that can be further improved.

  The silicone rubber composition of the present invention can be cured by heating to obtain a cured product having good solvent resistance. The silicone rubber product comprising the cured product of the silicone rubber composition of the present invention has excellent solvent resistance and can be expected to have the inherent heat resistance, cold resistance, weather resistance, and electrical insulation properties of the silicone rubber. Is expensive. In particular, since it does not easily expand even when it comes into contact with fuel oil such as engine oil, it can be suitably used for parts such as automobiles, vehicles, ships, airplanes and chemical plants.

Test pieces of Comparative Example 1, Examples 2 and 5 before and after immersion in xylene Test pieces of Comparative Example 1, Examples 2 and 5 before and after immersion in n-hexane

Claims (7)

(A) Formula (I):

(Where
R is independently R ¹ or R ² , of which at least two are R ¹ ,
R ¹ is independently a C ₂ -C ₆ alkenyl group,
R ² is independently a C ₁ -C ₆ alkyl group or a phenyl group, and 10 to 50 mol% of R ² is a phenyl group,
n is an average value of 10 to 2000) 100 parts by weight of a linear polyorganosiloxane represented by:
(B) Polyorganohydrogensiloxane having more than two hydrogen atoms bonded to silicon atoms in the molecule The number of hydrogen atoms bonded to silicon atoms for one alkenyl group present in (A) is 0.00. An amount of 5 to 10.0;
(C) Platinum group metal compound An amount containing 0.1 to 1,000 ppm by weight of platinum group metal atom relative to the amount of (A); and (D) An average particle diameter of 1 to 100 μm and an aspect ratio A solvent-resistant silicone rubber composition comprising 20 to 200 parts by weight of mica powder that is 10 to 500. The solvent-resistant silicone rubber composition according to claim 1, wherein R ¹ in (A) is a vinyl group.   The solvent resistant silicone rubber composition according to claim 1 or 2, wherein n in (A) is 20 to 1500. The solvent resistant silicone rubber composition according to any one of claims 1 to 3, wherein 30 to 50 mol% of R ² in (A) is a phenyl group.   A solvent-resistant silicone rubber product comprising a cured product of the solvent-resistant silicone rubber composition according to any one of claims 1 to 4.   The solvent-resistant silicone rubber product according to claim 5, which is a part for automobiles, vehicles, ships, airplanes or chemical plants.   The solvent-resistant silicone rubber product according to claim 5 or 6, which is an O-ring, packing or gasket.