JP6327083B2 - Antistatic silicone rubber composition, cured product thereof and method for producing the same - Google Patents

Description

The present invention is antistatic silicone rubber composition which gives a cured product having excellent antistatic property, to a cured product thereof and a manufacturing method thereof.

  Silicone rubber has excellent weather resistance, electrical properties, low compression set, heat resistance, cold resistance, and other properties, so it can be used in various fields including electrical equipment, automobiles, architecture, medical care, and food. Widely used. For example, keypads used as rubber contacts for remote controllers, typewriters, word processors, computer terminals, musical instruments, etc .; gaskets for construction; anti-vibration rubber for audio devices, etc .; automotive parts such as connector seals, spark plug boots, etc. Applications include packing for compact discs used, bread and cake molds. Currently, the demand for silicone rubber is increasing, and the development of silicone rubber having excellent characteristics is desired.

  These silicone rubbers are generally supplied in the form of a composition containing a highly polymerized organopolysiloxane and a reinforcing filler. This composition is prepared by mixing a reinforcing filler and various dispersants with a raw material polymer using a mixing apparatus such as a dough mixer and a two-roller. Reinforcing fillers such as organopolysiloxane and silica are electrically insulating materials, and the silicone rubber composition obtained by blending them and the cured silicone rubber are charged by contact with various substances, resulting in static electricity. There are problems such as generation of dust and adsorption of dust in the air.

  Conventionally, antistatic rubbers are polyether antistatic agents (Patent Document 1: JP 2002-500237 A) or carbon black (Patent Documents 2: 3, JP 2002-507240 JP, JP, 2002-327122, A) is used. When a polyether antistatic agent is used, there is a problem that the polyether is decomposed at a high temperature and a sufficient antistatic effect is not exhibited. In particular, it was actually the case that the antistatic effect was almost lost even by performing a known post cure with a cured product of a thermosetting silicone rubber composition. When carbon black is used, there is a problem that it is difficult to maintain electrical insulation or it is limited to black.

Japanese Patent Laying-Open No. 2003-82232 (Patent Document 4) proposes a silicone rubber composition for a semiconductive roller to which a lithium salt is added. In the semiconductive region, an electric wire that can be used only by an insulating material. There was a problem that it could not be applied to coatings or keypads.
In JP 2013-199509 A (Patent Document 5), an ionic liquid having an alkoxysilyl group is used, but since an ionic liquid having trifluorosulfonyl is used, it is strong when used at high temperatures. There is a risk of generating acidic trifluoromethanoic acid.

Special Table 2002-500237 Special table 2002-507240 gazette JP 2002-327122 A JP 2003-82232 A JP 2013-199509 A

  This invention is made | formed in view of the said situation, and provides the antistatic silicone rubber composition used as the silicone rubber (hardened | cured material) which can maintain the outstanding antistatic characteristic, its hardened | cured material, and its manufacturing method. It is for the purpose.

  As a result of intensive studies to achieve the above object, the present inventors have found that a silicone rubber composition having excellent antistatic performance can be obtained by adding a specific amount of polylactic acid to a thermosetting silicone rubber composition. As a result, the present invention was completed.

That is, the present invention provides the following antistatic silicone rubber composition, a cured silicone rubber obtained by heating and curing the composition, and a method for producing the same.
[1]
(A) Organopolysiloxane having at least two alkenyl groups in the molecule: 100 parts by mass
(B-1) Addition reaction curing agent comprising a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst: a hydrogen atom in which an organohydrogenpolysiloxane is bonded to a silicon atom with respect to one alkenyl group in the component (A) The amount of the hydrosilylation catalyst in terms of the platinum group metal amount is 1 mass ppm to 1 mass% with respect to the organopolysiloxane of component (A) and / Or (B-2) organic peroxide curing agent: 0.1 to 10 parts by mass,
And (C) Reinforcing Silica: The thermosetting silicone rubber composition containing 1 to 80 parts by mass is 100 parts by mass, and polylactic acid is contained in an amount of 0.001 to 10 parts by mass. An antistatic silicone rubber composition.
[2]
The antistatic silicone rubber composition according to [1], wherein the polylactic acid has an average degree of polymerization of 2 to 4,000.
[3]
The antistatic silicone rubber composition according to [1] or [2], wherein polylactic acid is blended into the thermosetting silicone rubber composition in the form of a paste in which polylactic acid is dispersed in advance in an organopolysiloxane.
[4]
The antistatic silicone rubber composition according to [1] or [2], wherein polylactic acid is blended into the thermosetting silicone rubber composition in the form of a solution previously dissolved in a solvent.
[5]
[1] A cured antistatic silicone rubber obtained by heat-curing the antistatic silicone rubber composition according to any one of [4].
[6]
[1] A method for producing a cured antistatic silicone rubber, comprising heat-molding the antistatic silicone rubber composition according to any one of [4] at 60 to 450 ° C.
[7]
Furthermore, the method for producing a cured antistatic silicone rubber according to [6], wherein secondary vulcanization is performed at 150 to 250 ° C.
[8]
The method for producing a cured antistatic silicone rubber according to [6] or [7] , wherein the antistatic silicone rubber composition is molded by any one of extrusion molding, press molding, and injection molding.

  The cured product of the antistatic silicone rubber composition of the present invention has excellent antistatic properties and can maintain excellent antistatic properties even when exposed to high temperatures. Moreover, coloring can also be made freely.

Hereinafter, the present invention will be described in detail.
The antistatic silicone rubber composition of the present invention is characterized in that 0.001 to 10 parts by mass of polylactic acid is contained in 100 parts by mass of the thermosetting silicone rubber composition.

The thermosetting silicone rubber composition is not particularly limited as long as it is a silicone rubber composition that cures by heating, but the organopolysiloxane (A) having at least two alkenyl groups in the molecule as a base polymer is used as a curing agent. (B) is preferably one using an addition reaction curing agent (B-1) and / or an organic peroxide curing agent (B-2). The shape may be a millable type or a liquid type. Liquid silicone rubber compositions are self-flowing at room temperature (usually 25 ° C. ± 10 ° C.), whereas millable silicone rubber compositions have high viscosity and are not self-flowing at room temperature. It means a raw rubber-like composition that is non-liquid (solid or highly viscous paste) and can be uniformly mixed under high shear stress by a kneading means such as a roll mill.
In the present invention, as a thermosetting silicone rubber composition constituting a matrix for blending and dispersing polylactic acid, typically, an addition reaction curable silicone rubber comprising only the following components (A) and (B-1): Examples thereof include an organic peroxide curable silicone rubber composition composed of only the composition and the following components (A) and (B-2). Furthermore, the co-vulcanization type silicone rubber composition which uses only addition reaction hardening and organic peroxide hardening which consist only of the following (A) component, (B-1) component, and (B-2) component is mentioned.

[(A) Organopolysiloxane having at least two alkenyl groups in the molecule]
As the component (A), those represented by the following average composition formula (I) can be used.
R _a SiO _{(4-a) / 2} (I)
(Wherein R is the same or different from each other, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and a is a positive number of 1.8 to 2.3.)

  Here, R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, which are the same or different from each other. Specifically, methyl, ethyl, propyl, isopropyl Group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group and other alkyl groups having 1 to 10 carbon atoms, phenyl group, tolyl group, Aryl groups having 6 to 10 carbon atoms such as xylyl group and naphthyl group, aralkyl groups having 7 to 10 carbon atoms such as benzyl group, phenylethyl group and phenylpropyl group, vinyl group, allyl group, propenyl group, isopropenyl group, Alkenyl groups having 2 to 10 carbon atoms such as butenyl group, hexenyl group, cyclohexenyl group and octenyl group, and some or all of hydrogen atoms of these groups Fluorine, bromine, halogen atom such as chlorine, those substituted with a cyano group or the like, such as chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group and the like. Among these, a methyl group, a vinyl group, a phenyl group, and a trifluoropropyl group are preferable, and 50 mol% or more of R, particularly 80 mol% or more, and particularly, all R except alkenyl groups are preferably methyl groups. .

  In addition, at least two of R must be alkenyl groups (preferably having 2 to 8 carbon atoms, more preferably 2 to 6). The alkenyl group content in R is preferably 0.0001 to 20 mol%, particularly 0.001 to 10 mol%. This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain, or may be bonded to both.

a is a positive number of 1.8 to 2.3, preferably 1.9 to 2.1, more preferably 1.98 to 2.02, and this organopolysiloxane basically has a main chain di-valent. It is a linear diorganopolysiloxane consisting of repeating organosiloxane units (R ₂ SiO _2/2 ) and having both molecular chain ends blocked with triorganosiloxy groups (R ₃ SiO _1/2 ). It may be partially branched as long as the elasticity is not impaired.

The molecular weight is not particularly limited, and can be used from a low-viscosity liquid to a high-viscosity raw rubber that does not self-flow at room temperature (25 ° C). The polymerization degree is preferably 100 to 100,000, particularly 150 to 20,000, and more preferably 2,000 to 20,000.
In the present invention, the degree of polymerization can be determined, for example, as a weight average molecular weight (weight average degree of polymerization) in terms of polystyrene by gel permeation chromatography analysis using toluene as a developing solvent.

Further, the liquid (oil-like) component (A) having self-fluidity at room temperature preferably has a viscosity at 25 ° C. of 50 to 1,000,000 mPa · s, particularly 100 to 100,000 mPa · s. .
The viscosity can usually be measured with a rotational viscometer (for example, BL type, BH type, BS type, cone plate type, etc.) at room temperature (25 ° C.) (hereinafter the same).

  As the component (A), the organopolysiloxane may be used alone or in combination of two or more having different molecular structures and polymerization degrees.

  Such an organopolysiloxane is subjected to ring-opening polymerization by a known method, for example, by (co) hydrolytic condensation of one or more organohalogenosilanes, or by using a cyclic polysiloxane with an alkaline or acidic catalyst. Can be obtained.

[(B) Curing agent]
Examples of the (B) curing agent include (B-1) addition reaction curing agent and (B-2) organic peroxide curing agent as described above.

(B-1) Addition reaction curing agent (B-1) As the addition reaction curing agent, an organohydrogenpolysiloxane and a hydrosilylation catalyst are used in combination.

The organohydrogenpolysiloxane includes 2 or more, preferably 3 or more, more preferably 3 to 200, and still more preferably 4 to 100, hydrogen atoms bonded to silicon atoms in one molecule (that is, SiH). Group), any of linear, cyclic, branched and three-dimensional network structures may be used, and a known organohydrogenpolysiloxane is used as a crosslinking agent for the addition reaction curable silicone rubber composition. For example, an organohydrogenpolysiloxane represented by the following average composition formula (II) can be used.
R ¹ _p H _q SiO _{(4-pq) / 2} (II)

In the above average composition formula (II), R ¹ represents an unsubstituted or substituted monovalent hydrocarbon group, which may be the same or different, and preferably excludes an aliphatic unsaturated bond. . Usually, those having 1 to 12 carbon atoms, particularly those having 1 to 8 carbon atoms are preferable. Specifically, alkyl groups such as methyl group, ethyl group and propyl group, cycloalkyl groups such as cyclohexyl group, phenyl groups, tolyl groups and the like. Aralkyl groups such as aryl group, benzyl group, 2-phenylethyl group and 2-phenylpropyl group, and groups in which part or all of hydrogen atoms of these groups are substituted with halogen atoms, for example, 3, 3, 3- Examples thereof include a trifluoropropyl group.
Note that p and q are 0 <p <3, preferably 0.5 ≦ p ≦ 2.2, more preferably 1.0 ≦ p ≦ 2.0, 0 <q ≦ 3, preferably 0.002 ≦ q. ≦ 1.1, more preferably 0.005 ≦ q ≦ 1, 0 <p + q ≦ 3, preferably 1 ≦ p + q ≦ 3, more preferably 1.002 ≦ p + q ≦ 2.7.

  Organohydrogenpolysiloxane has 2 or more, preferably 3 or more, SiH groups in one molecule, which may be present at both ends of the molecular chain or in the middle of the molecular chain. Also good. Moreover, as this organohydrogenpolysiloxane, it is preferable that the viscosity in 25 degreeC is 0.5-10,000 mPa * s, especially 1-300 mPa * s.

Specific examples of such organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (hydrogendimethylsiloxy). ) Methylsilane, tris (hydrogendimethylsiloxy) phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends trimethylsiloxy group-blocked Dimethylsiloxane / methylhydrogensiloxane copolymer, dimethylhydrogensiloxy-blocked dimethylpolysiloxane at both ends, dimethylhydrogensiloxy-blocked dimethylsiloxane at both ends Methyl hydrogen siloxane copolymer, both ends trimethylsiloxy group blocked methyl hydrogen siloxane / diphenyl siloxane copolymer, both ends trimethyl siloxy group blocked methyl hydrogen siloxane / diphenyl siloxane / dimethyl siloxane copolymer, both ends trimethyl siloxy group Blocked methylhydrogensiloxane / methylphenylsiloxane / dimethylsiloxane copolymer, both ends dimethylhydrogensiloxy group blocked methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer, both ends dimethylhydrogensiloxy group blocked methylhydrogensiloxane・ Dimethylsiloxane ・ Methylphenylsiloxane copolymer, (CH ₃ ) ₂ HSiO _1/2 unit and (CH ₃ ) ₃ SiO _1/2 unit And copolymers comprising SiO _4/2 units, (CH _{3) 2} HSiO _1/2 consisting of units and SiO _4/2 units, and copolymers thereof, (CH _{3) 2} HSiO _1/2 units and SiO _{4 /} Copolymers composed of ₂ units and (C ₆ H ₅ ) ₃ SiO _1/2 units, etc., and those obtained by substituting some or all of the methyl groups with other alkyl groups, phenyl groups, etc. in the above exemplified compounds In addition, compounds having the following structural formulas can be exemplified.

（式中、ｋは２〜１０の整数、ｓ及びｔは０〜１０の整数である。）

(In the formula, k is an integer of 2 to 10, and s and t are integers of 0 to 10.)

  As for the compounding quantity of the said organohydrogen polysiloxane, 0.1-40 mass parts is preferable with respect to 100 mass parts of (A) component. In addition, it is appropriate that the ratio of hydrogen atoms bonded to silicon atoms (≡SiH groups) is 0.5 to 10 for one aliphatic unsaturated bond (alkenyl group, diene group, etc.) of component (A). There is an appropriate range of 0.7-5. If the number is less than 0.5, crosslinking may not be sufficient, and sufficient mechanical strength may not be obtained. If the number exceeds 10, the physical properties after curing will be deteriorated, and particularly heat resistance and compression set will be reduced. It may get worse.

  The hydrosilylation catalyst is a catalyst that causes a hydrosilylation addition reaction between the alkenyl group of component (A) and the silicon atom-bonded hydrogen atom (SiH group) of the organohydrogenpolysiloxane. Examples of the hydrosilylation catalyst include a platinum group metal catalyst, which includes a simple substance of a platinum group metal and a compound thereof, and conventionally known catalysts for addition reaction curable silicone rubber compositions can be used. For example, platinum catalysts such as fine particles of platinum metal adsorbed on a support such as silica, alumina or silica gel, platinum chloride, chloroplatinic acid, chloroplatinic acid hexahydrate alcohol solution, palladium catalyst, rhodium catalyst, etc. Although mentioned, platinum or a platinum compound (platinum catalyst) is preferable.

  The addition amount of the catalyst only needs to accelerate the addition reaction, and is usually used in the range of 1 mass ppm to 1 mass% with respect to the organopolysiloxane of the component (A) in terms of the platinum group metal amount. A range of ˜500 ppm by mass is preferred. If the addition amount is less than 1 mass ppm, the addition reaction may not be sufficiently promoted and curing may be insufficient. On the other hand, if it exceeds 1 mass%, the addition of more than this will have little effect on the reactivity. It can be uneconomical.

(B-2) Organic peroxide curing agent (B-2) Examples of the organic peroxide curing agent include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, and o-methyl. Benzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,6 -Hexanediol-bis-t-butyl peroxycarbonate and the like.

  The addition amount of the organic peroxide is preferably 0.1 to 10 parts by mass, particularly preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the component (A). If the blending amount is too small, curing may be insufficient, and if it is too large, the cured silicone rubber may turn yellow due to the decomposition residue of the organic peroxide.

In addition, (A) component was combined with (B-1) component and (B-2) component in the range of the said compounding amount, respectively, and addition reaction hardening and organic peroxide hardening were used together. A co-vulcanized silicone rubber composition can also be obtained.
A commercially available thermosetting silicone rubber composition may be used.

[(C) Reinforcing silica]
(C) Reinforcing silica can be blended with the antistatic silicone rubber composition of the present invention as needed in order to impart mechanical strength and the like.
Examples of (C) reinforcing silica include fumed silica and precipitated (wet) silica. These silicas preferably has a specific surface area by the BET method is 50 m ² / g or more, are preferred in particular 100 to 400 m ² / g.
Such silica may be used by treating the surface with a surface treatment agent such as organopolysiloxane, silazane, chlorosilane, alkoxysilane, or the like, if necessary. Further, when the fine powder silica is blended with the organopolysiloxane of the component (A), the surface treatment agent may be blended simultaneously.

  (C) Although the mixture of component is arbitrary, the compounding quantity is 0-100 mass parts with respect to 100 mass parts of organopolysiloxane of (A) component, Preferably it is 1-80 mass parts, Most preferably, it is 5-5. 50 parts by mass. If the blending amount is too large, blending may be difficult, and rubber physical properties may be deteriorated.

  In addition, in the antistatic silicone rubber composition of the present invention, when an addition reaction curing agent (B-1) is used as the component (B), in addition to the catalyst of the component (B-1), hydrosilylation addition For the purpose of adjusting the curing rate by reaction, an addition reaction control agent may be used as long as the object of the present invention is not impaired. Specific examples include acetylene alcohol-based control agents such as ethynylcyclohexanol and tetracyclomethylvinylpolysiloxane.

[Other ingredients]
In the antistatic silicone rubber composition of the present invention, a filler such as pulverized quartz, crystalline silica, diatomaceous earth, and calcium carbonate, and a colorant are added to the above components as long as the object of the present invention is not impaired. , Tear strength improvers, heat resistance improvers such as iron oxide and cerium oxide, flame retardant improvers such as titanium oxide and platinum compounds, acid acceptors, heat conductivity improvers such as alumina and boron nitride, mold release agents Known as thermosetting silicone rubber compositions such as various alkoxysilanes, particularly phenyl group-containing alkoxysilanes and hydrolysates thereof, diphenylsilanediol, carbon functional silane, silanol group-containing low molecular weight siloxanes as dispersants for fillers It is optional to add other fillers and additives.

  The thermosetting silicone rubber composition and other optional components can be obtained by mixing the above components with a known kneader such as a kneader, a Banbury mixer, a two-roller, etc., but the component (C) is blended. In this case, it is usually preferable to add the curing agent of the component (B) after mixing the organopolysiloxane of the component (A) and the reinforcing silica of the component (C).

The polylactic acid used in the present invention may be any of D-form, L-form, and DL-form. Poly D-lactic acid, poly L-lactic acid, and poly DL-lactic acid can be produced by a conventionally known method. For example, it can be produced by a direct synthesis method from lactic acid (α-hydroxypropionic acid), a ring-opening polymerization method via lactide, or the like.
In the case of producing by direct dehydration condensation, L-lactic acid or D-lactic acid is subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably water is removed from the solvent distilled by azeotropic distillation. Polylactic acid can be obtained by a method of returning the substantially anhydrous solvent to the reaction system.
It is also known that polylactic acid can be obtained by subjecting L-lactide or D-lactide to ring-opening polymerization under reduced pressure in the presence of a metal-containing catalyst such as tin octylate.
Polylactic acid may be used individually by 1 type, and may use 2 or more types together.

  The polymerization degree of polylactic acid is 2 to 4,000, preferably 2 to 3,000. If the degree of polymerization is too high, it is difficult to add to the silicone rubber composition.

  In order to facilitate uniform dispersion and addition of polylactic acid in a silicone rubber composition (especially a millable silicone rubber composition), an organopolysiloxane (for example, alkenyl which is a base polymer of the component (A)) is previously prepared. You may add as a form of the antistatic paste which disperse | distributed polylactic acid in a part group-containing organopolysiloxane). In this case, the organopolysiloxane (for example, the base polymer) may be raw rubber or oily (liquid), but is preferably dispersed in the raw rubber-like organopolysiloxane from the viewpoint of forming a paste. Moreover, in order to improve workability | operativity, you may add fillers, such as reinforcing silica and diatomaceous earth, to this antistatic paste.

  The concentration of polylactic acid in the antistatic paste is preferably 0.5 to 90% by mass, more preferably 1 to 80% by mass, particularly preferably 1 to 70%, and further preferably 2 to 2% with respect to the whole antistatic paste. 50% by mass. If the concentration of polylactic acid is too low, the amount of the antistatic paste added may increase, and the physical properties of the cured silicone rubber may decrease, and if it is too high, it may be difficult to form a paste.

The preparation of the antistatic paste is preferably heat-treated at 100 ° C. or higher in order to improve the dispersibility of polylactic acid in the paste.
In addition, polylactic acid is used as an antistatic agent solution by dissolving polylactic acid in a solvent in order to improve dispersibility in a liquid antistatic silicone rubber composition that is liquid at room temperature and to exhibit a stable effect. It may be added. As the solvent, it is preferable to use ketones such as acetone and methyl ethyl ketone, and alcohols such as methanol and ethanol.

  The concentration of polylactic acid in the antistatic solution is preferably about 2 to 90% by mass, more preferably about 5 to 80% by mass, and still more preferably about 10 to 50% by mass with respect to the whole antistatic solution. If the polylactic acid concentration is too low, the amount of the antistatic agent solution added may increase, and the physical properties of the cured silicone rubber may be reduced. If it is too high, it may be difficult to dissolve.

  The addition amount of polylactic acid is 0.001 to 10 parts by mass, preferably 0.001 to 5 parts by mass, and more preferably 0.0015 to 1 part by mass with respect to 100 parts by mass of the thermosetting silicone rubber composition. More preferably, it is 0.002 to 0.5 parts by mass. When the amount is less than 0.001 part by mass, the antistatic effect is insufficient. When the amount is more than 10 parts by mass, the physical properties and heat resistance of the silicone rubber are adversely affected.

  Polylactic acid may be added to the thermosetting silicone rubber composition at the time of preparing the thermosetting silicone rubber composition, or the thermosetting silicone rubber composition already prepared in advance or the composition and other optional components. You may add at the time of component mixing manufacture.

  The antistatic silicone rubber composition of the present invention thus obtained becomes a silicone rubber having excellent antistatic properties by heat curing. As a molding method, a known molding method may be selected according to the shape and size of the target molded product. For example, methods such as injection molding, compression molding, injection molding, calendar molding, extrusion molding, coating, and screen printing are exemplified. The curing condition may be a known condition in the molding method, and is generally about 60 to 450 ° C., particularly 80 to 400 ° C., more preferably 120 to 200 ° C., for several seconds to 1 day. Further, for the purpose of reducing the compression set of the cured product, reducing the low-molecular siloxane component remaining in the silicone rubber, or removing the decomposition product of the organic peroxide, the temperature is 150 to 250 ° C. Preferably, post-curing (secondary vulcanization) may be performed in an oven at 200 to 240 ° C. for 1 hour or longer, preferably about 1 to 70 hours, and more preferably about 1 to 10 hours.

  As the antistatic performance of the obtained silicone rubber, static electricity was charged on the surface of the silicone rubber molded product by 6 kV by corona discharge using a static one meter (manufactured by Sisid Electric Co., Ltd.), and then the charged voltage was It is preferable that the halving time (half life) is within 2 minutes, particularly within 1 minute.

  By curing the antistatic silicone rubber composition of the present invention by the above method, yellowing of the cured product can be suppressed. In particular, by molding by any method of extrusion molding, press molding, injection molding, by heat molding at 60 to 450 ° C., particularly 80 to 400 ° C., or by secondary vulcanization at 150 to 250 ° C., Further yellowing suppression effect can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to a following example. The polymerization degree of siloxane is a weight average polymerization degree in terms of polystyrene by gel permeation chromatography analysis using toluene as a developing solvent, and the viscosity is measured by a rotational viscometer at room temperature (25 ° C.). The degree of polymerization (molecular weight) of polylactic acid is the weight average degree of polymerization (weight average molecular weight) in terms of polystyrene by gel permeation chromatography analysis using chloroform as a developing solvent.

The amount of charge and the presence or absence of yellowing were measured by the following methods.
Using a static amount meter (Static Static Electricity Co., Ltd.), the surface of a 6 mm thick silicone rubber sheet after post-curing at 200 ° C. for 4 hours and after post-curing at 200 ° C. for 24 hours by corona discharge After charging 6 kV, the time when the charged voltage was halved was measured.

An antistatic paste was prepared as follows.
[Preparation of antistatic paste 1]
100 parts by mass of thermosetting silicone rubber composition KE-571-U (manufactured by Shin-Etsu Chemical Co., Ltd.), 1 part by mass of poly DL lactic acid (manufactured by Wako Pure Chemical Industries, Ltd., Mw 6,000 to 16,000) Then, the mixture was kneaded at 150 ° C. for 10 minutes to prepare an antistatic agent paste 1.

[Preparation of Antistatic Agent Solution 1]
20 parts by mass of poly DL lactic acid (manufactured by Wako Pure Chemical Industries, Ltd., Mw 6,000 to 16,000) was uniformly dissolved in 80 parts by mass of acetone to prepare an antistatic agent solution 1.

[Example 1]
100 parts by mass of an organopolysiloxane raw rubber comprising 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, 0.025 mol% of dimethylvinylsiloxy units and having an average degree of polymerization of about 6,000, BET 45 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g, a silanol group at both ends as a dispersant, an average polymerization degree of 15 and a viscosity at 25 ° C. of 30 mPa · s is 10 parts by weight of dimethylpolysiloxane, 0.15 parts by weight of poly DL lactic acid (manufactured by Wako Pure Chemical Industries, Ltd., Mw 6,000 to 16,000) is added and kneaded in a kneader at 170 ° C. The composition (base compound 1) was prepared by heat treatment for 2 hours.
To 100 parts by mass of this composition (base compound 1), 0.4 parts by mass of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane as a cross-linking agent was added by a two-roll. After uniformly mixing to produce a raw rubber-like silicone rubber composition, the composition was press-cured for 10 minutes at 165 ° C. and 70 kgf / cm ² to prepare a 6 mm thick sheet. Next, post-curing for 4 hours and post-curing for 24 hours were performed in an oven at 200 ° C.
The silicone rubber was returned to room temperature, and the charge amount (half life) was measured. The results are shown in Table 1.

[Example 2]
100 parts by mass of an organopolysiloxane raw rubber comprising 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, 0.025 mol% of dimethylvinylsiloxy units and having an average degree of polymerization of about 6,000, BET 45 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g, a silanol group at both ends as a dispersant, an average polymerization degree of 15 and a viscosity at 25 ° C. of 30 mPa · 10 parts by mass of dimethylpolysiloxane s was added, kneaded with a kneader, and heat-treated at 170 ° C. for 2 hours to prepare a composition (base compound 2).
10 parts by weight of antistatic paste 1 and 90 parts by weight of this composition (base compound 2), 0.4 parts by weight of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane as a crosslinking agent Parts were added with two rolls and mixed uniformly to produce a raw rubber-like silicone rubber composition, and then the composition was press-cured at 165 ° C. and 70 kgf / cm ² for 10 minutes to obtain a 6 mm thickness A sheet of was prepared. Next, post-curing for 4 hours and post-curing for 24 hours were performed in an oven at 200 ° C.
The silicone rubber was returned to room temperature, and the charge amount (half life) was measured. The results are shown in Table 1.

[Example 3]
The charge amount (half life) was measured in the same manner as in Example 1 except that the addition amount of the antistatic agent paste 1 was 20 parts by mass. The results are shown in Table 1.

[Example 4]
The amount of charge (half life) was measured in the same manner as in Example 1 except that poly L lactic acid (Mw 1,600-2,400, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of poly DL lactic acid. The results are shown in Table 1.

[Example 5]
40 parts by mass of dimethylpolysiloxane blocked with dimethylvinylsiloxy group at both ends of a molecular chain having a viscosity of 1,000 mPa · s, 40 parts by mass of dimethylpolysiloxane blocked with dimethylvinylsiloxy at both ends of a molecular chain having a viscosity of 5,000 mPa · s, main chain A diorganosiloxane unit comprising 5 mol% of methyl vinyl siloxane units and 95 mol% of dimethyl siloxane units, and having a viscosity of 700 mPa · s and having a molecular chain at both ends trimethylsiloxy group-blocked dimethyl siloxane / methyl vinyl siloxane copolymer 20 parts by mass of coalescence, 20 parts by mass of hydrophobized fumed silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 110 m ² / g, both ends of a molecular chain having a viscosity of 50 mPa · s Trimethylsiloxy group-blocked methyl hydrogen polysiloxane Hydrogen atoms bonded to elementary atoms: 1.14% by mass) 5.0 parts by mass, molecular chain both ends dimethylhydrogen having a viscosity of 25 mPa · s and SiH groups in the middle of the molecular chain (side chain) Siloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer (hydrogen atom bonded to silicon atom: 0.54% by mass) 2.2 parts by mass [in the composition relative to the total of silicon atom-bonded vinyl groups in the composition SiH group total molar ratio; SiH / SiVi = 3.7 mol / mol], 1.60 parts by mass of antistatic agent solution 1, 0.03 parts by mass of 1-ethynylcyclohexanol, chloroplatinic acid and divinyltetra A liquid silicone rubber composition in which a complex of methyldisiloxane is added in an amount of 15 ppm in terms of mass of platinum metal to the total of vinyl group-containing organopolysiloxane. It was prepared.
This composition was press-cured for 10 minutes under the conditions of 120 ° C. and 100 kgf / cm ² to prepare a 6 mm thick sheet. Next, post-curing for 4 hours and post-curing for 24 hours were performed in an oven at 200 ° C.
The silicone rubber was returned to room temperature, and the charge amount (half life) was measured. The results are shown in Table 1.

[Comparative Example 1]
The charge amount (half-life) was measured in the same manner as in Example 1 except that poly DL lactic acid was not added. The results are shown in Table 1.

[Comparative Example 2]
The charge amount (half-life) was measured in the same manner as in Example 5 except that the antistatic agent solution 1 was not added. The results are shown in Table 1.

[Comparative Example 3]
Example 5 was repeated except that 0.4 parts by mass of a polyether-modified silicone oil (KF351F manufactured by Shin-Etsu Chemical Co., Ltd.) having a viscosity of 75 mPa · s at 25 ° C. was added instead of the antistatic agent solution 1. The charge amount (half life) was measured. The results are shown in Table 1.

Claims (8)

(A) Organopolysiloxane having at least two alkenyl groups in the molecule: 100 parts by mass
(B-1) Addition reaction curing agent comprising a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst: a hydrogen atom in which an organohydrogenpolysiloxane is bonded to a silicon atom with respect to one alkenyl group in the component (A) The amount of the hydrosilylation catalyst in terms of the platinum group metal amount is 1 mass ppm to 1 mass% with respect to the organopolysiloxane of component (A) and / Or (B-2) organic peroxide curing agent: 0.1 to 10 parts by mass,
And (C) Reinforcing Silica: The thermosetting silicone rubber composition containing 1 to 80 parts by mass is 100 parts by mass, and polylactic acid is contained in an amount of 0.001 to 10 parts by mass. An antistatic silicone rubber composition.   The antistatic silicone rubber composition according to claim 1, wherein the average degree of polymerization of the polylactic acid is 2 to 4,000.   The antistatic silicone rubber composition according to claim 1 or 2, wherein polylactic acid is blended into the thermosetting silicone rubber composition in the form of a paste previously dispersed in organopolysiloxane.   The antistatic silicone rubber composition according to claim 1 or 2, wherein polylactic acid is added to the thermosetting silicone rubber composition in the form of a solution previously dissolved in a solvent.   An antistatic silicone rubber cured product obtained by heat-curing the antistatic silicone rubber composition according to any one of claims 1 to 4.   A method for producing a cured antistatic silicone rubber, comprising heat-molding the antistatic silicone rubber composition according to any one of claims 1 to 4 at 60 to 450 ° C.   Furthermore, the manufacturing method of the antistatic silicone rubber hardened | cured material of Claim 6 which performs secondary vulcanization | cure at 150-250 degreeC. The method for producing a cured antistatic silicone rubber according to claim 6 or 7 , wherein the antistatic silicone rubber composition is molded by any one of extrusion molding, press molding, and injection molding.