JPH08887B2 - Addition vulcanization type silicone rubber composition and cured product thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides an addition vulcanizing type silicone rubber composition, particularly a molded product having a long pot life after kneading with a curing agent and a catalyst, and without foaming. The present invention also relates to an addition-vulcanizable silicone rubber composition and a cured product thereof, which are useful for extrusion molded parts such as medical parts and tubes because of their excellent transparency and extrusion moldability.

(Prior Art) Silicone rubber is widely used as a medical part because it has excellent heat resistance, cold resistance, and weather resistance, gives a transparent molded body, and is excellent in biocompatibility. Silicone rubber used in various fields is generally considered to be an addition vulcanization type. However, when this addition vulcanization type silicone rubber is kneaded with a crosslinking agent and a catalyst, vulcanization proceeds even at room temperature. Usually, a vulcanization retarder (control agent) such as benzotriazole, an acetylene alcohol derivative, and triphenyl phosphite is appropriately added to this.

(Problems to be solved by the invention) However, this addition vulcanization type silicone rubber has a sufficient working life in order to extrude a composition and vulcanize it by normal pressure hot air vulcanization (HAV). When the above-mentioned control agent is added so that foaming is often observed in this extruded product, in order to suppress this foaming, the amount of the catalyst is increased, the control agent is decreased, or the compound is plasticized. If the degree of increase is high, there is a disadvantage that the pot life becomes short, the extrusion characteristics are significantly impaired, the workability becomes poor, and the appearance of the molded product becomes poor.

(Means for Solving the Problems) The present invention relates to an addition vulcanizing type silicone rubber composition and a cured product thereof in which such disadvantages are solved. (Wherein R ¹ is the same or different and is an unsubstituted or substituted monovalent hydrocarbon group, a is a positive number from 1.98 to 2.01) and is an alkenyl group bonded to at least two silicon atoms in one molecule. Containing 100 parts by weight of an organopolysiloxane having a degree of polymerization of 3,000 or more, B) containing an average of more than 2 hydrogen atoms (≡SiH groups) bonded to a silicon atom in one molecule, A) above. Organopolysiloxane as a component, component (D) to be described later, C) specific surface area of C) in the amount of 0.5 to 4 ≡SiH groups to the total of one alkenyl group in component (E) 5 to 100 parts by weight of reinforcing silica filler of 150 m ² / g or more, D) General formula R ² _b Si (OR
³ ) _(4-b) (wherein R ² is the same or different, unsubstituted or substituted monovalent hydrocarbon group, R ³ is an alkyl group or an alkoxyalkyl group having 1 to 6 carbon atoms, and b is 0 to 3 An integer) alkoxysilane or a partial hydrolyzate thereof 0.5 to 2
0 parts by weight, E) General formula R ⁴ _c SiCl _4-c (wherein R ⁴ is the same or different, unsubstituted or substituted monovalent hydrocarbon group, and c is 1 to
Organochlorosilane 10 to 5,000p represented by 3)
pm, F) 10 to 5,000 ppm of a platinum-based catalyst selected from platinum or a platinum compound.

That is, the present inventors have conducted various studies to develop an addition vulcanization type silicone rubber composition which does not have the above-mentioned disadvantages, and as a result, the conventional composition comprising the above-mentioned components A), B), C) and F) has been obtained. Addition of the above-mentioned alkoxysilane or its partial hydrolyzate as the component D) and organochlorosilane as the component E) to a known addition vulcanizing type silicone rubber composition improves the transparency of the composition,
It has been found that even if the above-mentioned control agent is added, it is extruded, and the convenience that foaming does not occur when HAV vulcanized is given, and therefore it has excellent transparency. The present invention was completed by confirming that an addition vulcanizing type silicone rubber composition having a long pot life after addition of a curing agent and a catalyst and having no foaming and having excellent extrusion moldability can be obtained. It was

 This will be described in more detail below.

(Function) The present invention relates to an addition vulcanization type silicone rubber composition having improved physical properties and a cured product thereof.

The organopolysiloxane as component A) constituting the addition-vulcanized silicone rubber composition of the present invention has an average composition formula R ¹ is a methyl group, an ethyl group, a propyl group, a butyl group, an alkyl group such as an octyl group, a cycloalkyl group such as a cyclohexyl group, a vinyl group, an alkenyl group such as an allyl group, a phenyl group, a tolyl group, etc. An aryl group of
Or from a chloromethyl group in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with a halogen atom, a cyano group, a 3,3,3-trifluoropropyl group, a 2-cyanoethyl group, etc. The same or different, unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, which is selected, and a is a positive number of 1.98 to 2.1, Since this composition is of the addition vulcanization type, it is necessary that it has an alkenyl group bonded to at least two silicon atoms in one molecule, which also has a degree of polymerization. Is 3,
If it is less than 000, the extrusion processability will be inferior, and the resulting molded article will have poor mechanical strength and inferior molding processability, so the polymerization degree will be 3,000 or more and an essentially linear diorganopolyester will be obtained. It is required to be siloxane, which may partially include a branched structure.

Further, the organohydrogenpolysiloxane as the component B) which constitutes the addition vulcanization type silicone rubber composition acts as a cross-linking agent for the component A), which is the organopolysiloxane as the component A). A hydrogen atom (≡SiH group) bonded to a silicon atom is added to the alkenyl group as an aliphatic unsaturated group in the presence of a platinum catalyst as a component F) described below. This averages 2 ≡SiH groups in one molecule.
It is necessary to have more than 3 and preferably at least 3 and therefore HSiO _3/2 , C
Siloxane units having ≡SiH bond such as H ₃ HSiO and (CH ₃ ) ₂ HSiO _1/2 and SiO ₂ , CH ₃ SiO _3/2 , C ₆ H ₅ SiO _3/2 , (CH ₃ ) ₂ S
_{iO, CH 3 C 6 H 5} SiO, (C 6 H 5) 2 -SiO, (CH 3) 3 is made of a siloxane units such as SiO _1/2 are exemplified, specifically methylhydrodiene Copolymers of enepolysiloxane and dimethylhydrogenpolysiloxane, Copolymers of methylhydrogenpolysiloxane and methylphenylpolysiloxane, Copolymers of methylhydrogenpolysiloxane, dimethylpolysiloxane and diphenylpolysiloxane, ( CH ₃ ) _2- HSiO _1/2 , CH ₃ SiO
Usually, a copolymer composed of _3/2 , (CH ₃ ) ₂ SiO and SiO ₂ and having 400 or less silicon atoms in one molecule is exemplified.

The organohydrogen polysiloxane is added in an amount of 0.5 to 0.5 ≡SiH bond with respect to one total of the alkenyl groups bonded to the silicon atoms present in the components A), D) and E) described below. It is necessary to supply enough for four pieces.

Next, since the silica filler as the component C) constituting the addition reaction type silicone rubber composition of the present invention is used for reinforcing the intended silicone rubber molded article, the specific surface area is 150 m ² / g. More than that is needed. As this silica filler, fumed silica,
Precipitating silica and the like are exemplified, but the surface of these may be pretreated with silane, siloxane, silazane or the like. The amount of the silica filler added is less than 5 parts by weight based on 100 parts by weight of the organopolysiloxane as the component A) and the strength is too low.
Processability is not obtained, and if it is more than 100 parts by weight, it is difficult to mix it into the composition, the composition becomes hard and the moldability decreases, and the mechanical strength of the cured product becomes poor. Therefore, the amount is required to be in the range of 5 to 100 parts by weight, and the preferable range is 10 to 80 parts by weight.

The alkoxysilane or its partial hydrolyzate as component D) which constitutes the addition vulcanizing type silicone rubber composition of the present invention has a general formula of R ² _b Si (OR ³ ) _4-b (2) , R ² is the same as or different from R ¹ described above,
Usually, an unsubstituted or different monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8, R ³ is an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, a butyl group, or methoxy. Methyl group, methoxyethyl group, ethoxyethyl group,
An alkoxyalkyl group such as an ethoxymethyl group,
b is assumed to be an integer from 0 to 3, and si (OC
_{H 3) 4, Si (OC} 2 H 5) 4, CH 3 Si (OCH 3) 3, CH 3 Si (OC 2
_{H 5) 3, CH 3 Si} (OC 3 H 7) 3, CH 3 Si (OC 2 H 4 OCH 3) 3,
(CH ₃ ) ₂ Si (OCH ₃ ) ₂ , (CH ₃ ) ₂ Si (OC ₂ H ₅ ) ₂ , (C
H ₃ ) ₃ SiOCH ₃ , (CH ₃ ) ₃ SiOC ₂ H ₅ , CH ₂ = CHSi (OC
_{H 3) 3, CH 2 =} CHSi (OC 2 H 5) 3, (CH 3) (CH 2 = CH) Si
_{(OCH 3) 2, (CH} 3) (CH 2 = CH) Si (OC 2 H 5) 2, (C
_{H 3) 2 (CH 2 =} CH) SiOCH 3, (CH 3) 2 (CH 2 = CH) SiOC 2
_{H 5, C 6 H 5 Si} (OCH 3) 3, C 6 H 5 Si (OC 2 H 5) 3, (CH 3)
_{(C 6 H 5) Si (} OCH 3) 2, (CH 3) (C 6 H 5) Si (OC
₂ H ₅ ) ₂ , (CH ₃ ) ₂ (C ₆ H ₅ ) SiOC ₂ H ₄ OCH ₃ , CF ₃ CH ₂ CH ₂ Si
(OCH ₃ ) ₃ , CF ₃ CH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃ , CF ₃ CH ₂ CH ₂ Si (O
_{C 3 H 7) 3, CF} 3 CH 2 CH 2 (CH 3) Si (OCH 3) 2, CF 3 CH 2 CH 2
_{(CH 3) Si (OC 2} H 5) 2 , etc. and their partial hydrolysis is illustrated.

The amount of this compound added is less than 0.5 parts by weight based on 100 parts by weight of the organopolysiloxane as component A), and the transparency of the composition is not improved.
When this composition is extrusion-molded and HAV-vulcanized, the effect of preventing foaming does not appear, and if it exceeds 20 parts by weight, the viscosity of this composition decreases and moldability such as roll processability and extrusion processability is reduced. Since it becomes inferior and the mechanical strength of the molded product obtained from this deteriorates, it is necessary to set this in the range of 0.5 to 20 parts by weight.

Further, the organochlorosilane as the component E) constituting the addition vulcanizing type silicone rubber composition of the present invention has a general formula represented by R ⁴ _c SiCl _4-c (3), and R ⁴ is R ¹ Same or different, similar to
Usually, it is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, wherein C is an integer of 1 to ₃ , and CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiCl ₂ , (C
H ₃ ) ₃ SiCl, C ₂ H ₅ SiCl ₃ , (C ₂ H ₅ ) ₂ SiCl ₂ , (C ₂ H ₅ ) ₃ SiC
_{l, CH 2 = CHSiCl 3 (} CH 2 = CH) (CH 3) SiCl 2, (CH 2 = C
H) (CH ₃ ) ₂ SiCl, C ₆ H ₅ SiCl ₃ , (CH ₃ ) (C ₆ H ₅ ) SiCl ₂ ,
(C ₆ H ₅ ) ₂ SiCl ₂ , (CH ₃ ) ₂ (C ₆ H ₅ ) SiCl, CF ₃ CH ₂ CH ₂ Si
Cl ₃ , CF ₃ CH ₂ CH ₂ (CH ₃ ) SiCl ₂ , CF ₃ CH ₂ CH ₂ (CH ₃ ) ₂ SiCl
Are exemplified.

The addition amount of this organochlorosilane is too small if it is less than 10 ppm with respect to 100 parts by weight of the above-mentioned organopolysiloxane as the component A), and the synergistic effect with the above-mentioned alkoxysilane as the component D) or its partial hydrolyzate. The effect of improving transparency of this composition, the effect of preventing foaming by extrusion molding and HAV vulcanization of this composition cannot be obtained, and when it is more than 5,000 ppm, viscosity decrease due to cracking of organopolysiloxane as component A) and It is necessary to set this in the range of 10 to 5,000 ppm because coloring is observed and moldability and transparency become poor.

The mechanism by which the addition of the D) and E) components gives the composition improved transparency and an effect of preventing foaming during vulcanization is not necessarily clear, but the addition of the E) component causes hydrolysis of the D) component. It is considered that the property and the reactivity with silica are promoted, the degree of treatment of the silica surface is increased to make the silica hydrophobic, the compatibility with the organopolysiloxane is improved, and the adsorbed water is further removed.

The platinum-based catalyst as the component F) constituting the addition vulcanizing type silicone rubber of the present invention is an organopolysiloxane as the component A), an alkoxysilane as the component D) or a partial hydrolyzate thereof, E). This is for promoting the addition reaction between the alkenyl group contained in the organochlorosilane as a component and the ≡SiH bond contained in the organohydrogenpolysiloxane as the B) component. Examples thereof include platinum black, chloroplatinic acid, alcohol modified chloroplatinic acid, complex salts of chloroplatinic acid with ethylene or propylene, and complex salts of chloroplatinic acid with vinyl siloxane. The amount of platinum is 10 to 10 parts by weight based on 100 parts by weight of the organopolysiloxane as the component A).
The range may be 5,000 ppm, preferably 50 to 1,000 ppm.

The addition reaction vulcanizing type silicone rubber composition of the present invention can be obtained by uniformly mixing the predetermined amounts of the above-mentioned components A) to F), and this mixing is performed by mixing these components with a roll, a kneader, a Banbury mixer, etc. The mixture may be kneaded by using a mixer of (1), but this mixing is generally performed by adding a reinforcing silica filler as component C) to the organopolysiloxane of component A) and an alkoxysilane or a partial hydrolyzate thereof as component D). E) Organochlorosilane as a component is mixed beforehand and uniformly kneaded, and then 120 to 200 ° C
After heating for about 30 minutes to 6 hours, filter through a screen of 150 to 200 mesh, and then knead the organohydrogenpolysiloxane as component B) and the platinum catalyst as component F). Good. In addition,
It is optional to add a conventionally known addition reaction control agent such as benzotriazole, an acetylene alcohol derivative, and triphenyl phosphite to this composition, according to which the pot life is set to an arbitrary length. It can be adjusted, and it is optional to add a known heat resistance improver, various carbon functional silanes and the like.

The addition vulcanization type silicone rubber composition of the present invention thus obtained has the characteristics of a curing agent, a catalyst, a long pot life after kneading, and excellent moldability. Molding is performed, for example, by extruding this from a die using an extruder used for molding silicone rubber, molding it, and then allowing it to stay in a heating cylinder set at 250 to 450 ° C. for 10 to 60 seconds to cure and cure it. The molded product has a desired shape. It should be noted that this product has excellent properties such as heat resistance, cold resistance, weather resistance, electrical properties, and compression resilience similar to general silicone rubber. In particular, extruded products do not have foam in the molded body. Since it has an advantage that it has excellent transparency, it is particularly suitable as a medical component, and further as a tube or the like.

(Examples) Next, examples of the present invention and comparative examples will be given. In the examples, parts are parts by weight and viscosity is a measured value at 25 ° C.

Examples 1 and 2, Comparative Example 1 Dimethyl siloxane unit 99.92 mol%, methyl vinyl siloxane unit 0.08 mol%, the end of the molecular chain was blocked with dimethyl vinyl siloxy group, the average degree of polymerization is about.
97 parts of 8,000 methyl vinyl polysiloxanes, 90 mol% of dimethyl siloxane units and methyl vinyl siloxane units
Organopolysiloxane consisting of 3 parts of methylvinylpolysiloxane having an average degree of polymerization of about 5,000 and having a molecular chain end blocked with a dimethylbitylsiloxy group and having a specific surface area of 200 m ² / g. Fumed silica 3
6 parts of dimethyldimethoxysilane _{(CH 3) 2 Si (OCH} 3) 2 10
Parts, 3 parts of an α, ω-dimethylpolysiloxane-diol having a viscosity of 15 cS and the amount of dimethyldichlorosilane (CH ₃ ) ₂ SiCl ₂ shown in Table 1 are added and uniformly mixed using a kneader mixer, A compound (C) was prepared by heat-treating at 170 ° C. for 2 hours to prepare compounds (A) and (B) and having the same composition as above except that this dimethyldichlorosilane was not added.

Then, the compounds (A) to (C) were dispensed into a sheet having a thickness of 5 mm on two rolls and placed in an oven at 250 ° C for 3 minutes to examine the foaming state of the unvulcanized dough.
As shown in Table 1, the compounds (A) and (B) did not have foaming, but the compound (C) had fine foaming as a whole.

Next, this compound (A), (B), (C) 100
To the department After adding 1.3 parts of methylhydropolysiloxane, 0.05 part of ethynylcyclohexanol as an addition reaction control agent and 100 ppm of platinum, and kneading with a two-roll mill, an unvulcanized dough having a thickness of about 2 mm was separated. After press molding under conditions of 20 ° C and 20 kgf / cm ² for 10 minutes and then secondary vulcanization at 200 ° C for 4 hours to prepare test pieces and examine their physical properties, the results are as shown in Table 1. Was obtained, and the unvulcanized dough that had been dispensed to a thickness of about 5 mm was heat cured in a vulcanization tower at 400 ° C. for 30 seconds, and the foaming state was examined. The results as shown in Table 1 were obtained. was gotten.

Examples 3 to 5 Treatment was carried out in the same manner as in Example 1 except that trimethylchlorosilane (CH ₃ ) ₃ SiCl was used as the organochlorosilane as the component E) in Example 1 and was added in the amount shown in Table 2. Compounds (D), (E) and (F) were prepared, and the same tests as in Example 1 were carried out using the compounds, and the results as shown in Table 2 were obtained.

Example 6, Comparative Examples 2 to 3 The compound (A) prepared in Example 1 and the compound (C) prepared in Comparative Example 1 were added to the methylhydrogen polysiloxane used in Example 1 and an addition reaction control agent. Ethynylcyclohexanol and platinum as a catalyst were added in the amounts shown in Table 3 to make an addition vulcanization type silicone rubber composition, which was heated in a vulcanization tower at 400 ° C for 30 seconds to cure HAV vulcanization. When the foaming state when the composition was allowed to stand and the pot life when the composition was left at room temperature were examined, the results as shown in Table 3 were obtained, and the addition vulcanization type silicone rubber composition of the present invention was foamed. It was confirmed that the workability was long and the workability was excellent.

(Effects of the Invention) The present invention relates to an addition vulcanization type silicone rubber composition excellent in transparency and extrusion processability and a cured product thereof, which is, as described above, A) alkenyl group-containing organopolysiloxane, B). ) Organohydrogenpolysiloxane, C) Reinforcing silica filler, D) Alkoxysilane or partial hydrolyzate thereof, E) Organochlorosilane, F) Platinum-based catalyst, which is A). , B), C) and F) are added to a known composition containing an alkoxysilane or a partial hydrolyzate thereof as a component D) and an organochlorosilane as a component E), the composition is transparent. Of the addition reaction control agent is eliminated and the foaming at the time of vulcanization is also eliminated. The advantage is that an addition vulcanizing type silicone rubber composition having excellent transparency and extrusion moldability, which gives a molded article free from bubbles, can be obtained.

Claims (2)

[Claims] 1. A) Average composition formula R ¹ _a SiO _{(4-a) / 2} (wherein R ¹ is the same or different, unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number from 1.98 to 2.01. ) Organopolysiloxane having a degree of polymerization of 3,000 or more and containing an alkenyl group bonded to at least two silicon atoms in one molecule.
00 parts by weight, B) A hydrogen atom (≡SiH) bonded to a silicon atom in one molecule.
An organopolysiloxane as component A), which contains an average of more than 2 groups), component D) described below, component E).
For one total alkenyl group contained in the component
Organohydrogenpolysiloxane in an amount to supply 0.5 to 4 ≡SiH groups, C) Reinforcing silica filler 5-1 having a specific surface area of 150 m ² / g or more
00 parts by weight, D) General formula R ² _b Si (OR ³ ) _(4-b) (wherein R ² is the same or different, unsubstituted or substituted monovalent hydrocarbon group, and R ³ is 1 to 6 carbon atoms. Alkyl group or alkoxyalkyl group of, b is an integer of 0 to 3) alkoxysilane or a partial hydrolyzate thereof represented by 0.5 to 20 parts by weight, E) the general formula R ⁴ _c SiCl _(4-c) (where R is ⁴ is the same or different, unsubstituted or substituted monovalent hydrocarbon group, c is an organochlorosilane represented by 1 to 3) 10 to 5,000 ppm, F) Platinum catalyst 10 selected from platinum or a platinum compound
Up to 5,000 ppm, and an addition vulcanization type silicone rubber composition. 2. A cured product obtained by curing the composition according to claim 1.