KR20130075023A

KR20130075023A - Heat curable silicone rubber compositions and manufacturing method of the same

Info

Publication number: KR20130075023A
Application number: KR1020110143202A
Authority: KR
Inventors: 송수용; 정효성
Original assignee: 주식회사 케이씨씨
Priority date: 2011-12-27
Filing date: 2011-12-27
Publication date: 2013-07-05

Abstract

The present invention is 100 parts by weight of silicone gum; 10 to 100 parts by weight of reinforcing silica; 0.5 to 20 parts by weight of a silicon-based processing aid having a functional group at its end; Disclosed is a thermosetting silicone rubber composition comprising a boric acid compound and a borate compound, 0.01 to 5 parts by weight of a surface strength enhancer including at least one selected from the group consisting of boric acid compounds and a mixture thereof.

Description

Heat curable silicone rubber compositions and manufacturing method of the same

The present invention relates to a thermosetting silicone rubber composition and a method of manufacturing the same, and more particularly, to a thermosetting silicone rubber composition having excellent surface strength and a method of manufacturing the same.

Conventional silicone rubber is a rubber composition that is cured with an organic peroxide curing agent can be used in various applications, excellent stability of high temperature and low temperature, and various hardness can be expressed. Furthermore, it has the advantage of excellent chemical stability, water repellency, electrical properties and compression resistance. The general silicone rubber composition is preferably prepared by applying a reinforcing filler such as high viscosity silicone gum and fumed silica containing intramolecular vinyl groups and processing aids. A reinforcing filler is necessary to give mechanical strength to a weak silicone gum and to increase the surface strength of the product. Rubber containing high silica, which has high surface strength, hardens itself during storage, and becomes brittle, and has a solidification phenomenon. In order to prevent such solidification phenomenon, a low-polymerization sock end hydroxy monomolecular polymer ( polymer is applied properly. When used in excess, the solidification is eliminated, but the surface strength is reduced, so the workability deteriorates in the roll dispersing process and the forming and cutting process. Therefore, an appropriate amount should be used. The silicone rubber composition may disperse the organic peroxide curing agent to raise the temperature to obtain a final rubber product in a desired form.

Conventionally, according to Korean Patent Publication No. 558,957, in the rubber composition for tires, high surface strength is realized by using a trade name PAX Plus PE including high-density polyethylene modified with rubber as a surface strength enhancer. It cannot be applied to the silicone rubber composition because it is incompatible with and degrades thermal stability. U.S. Patent Publication No. 5,721,300 used ammonium, alkali metal or alkaline metal carbamate to obtain silicone rubber compositions with high surface strength and low compression set, but these materials can cause yellowing in silicone rubber compositions. It has a disadvantage.

The present invention was derived to solve the above-mentioned problems, the object of the present invention is to maintain the content of the appropriate silica and processing aids, while having a high surface strength does not affect the physical properties after curing storage stability, roll, molding And it relates to a thermosetting silicone rubber composition and its manufacturing method that does not affect the product properties after curing while maintaining workability in the cutting process.

Thermosetting silicone rubber composition according to an embodiment of the present invention,

100 parts by weight of a silicon gum; 10 to 100 parts by weight of reinforcing silica;

0.5 to 20 parts by weight of a silicon-based processing aid having a functional group at its end;

0.01 to 5 parts by weight of a surface strength improving agent comprising a mixture of at least one or more of a boric acid compound and a borate compound.

At this time, the boric acid compound is boric acid having a concentration of 90% or more of boric acid (H3BO3) or powdered boric acid having a purity of 99.5% or more, the borate compound is characterized in that the triethyl borate having a purity of 97.0% or more of the liquid form.

In addition, the silicon gum has a repeating unit represented by RaSiO (4-a) / 2. (Wherein R is an aliphatic saturated hydrocarbon group or aliphatic unsaturated hydrocarbon group having 1 to 10 carbon atoms or an aromatic unsaturated hydrocarbon group having 6 to 30 carbon atoms, and a has a value of 1.90 to 2.05)

In addition, the reinforcing silica has a specific surface area of 180 to 240 m 2 / g, dry silica having an average particle size of 7 to 22 nm, and specific gravity of 1.9 to 2.2 g / cm 3.

In addition, the processing aid may be a low viscosity polyorganosiloxane polymer having a structure of R5Y-SiR1R2 (OSiR3R4) n-YR5. Wherein R 1, R 2, R 3 and R 4 are each independently any one selected from the group consisting of an alkyl group, a vinyl group and a phenyl group, wherein the alkyl group has 1 to 10 carbon atoms; Y is O, NH or NR 6, Wherein R 6 is an alkyl group having 1 to 10 carbon atoms; R 5 is hydrogen or an alkyl group wherein the alkyl group has 1 to 10 carbon atoms and n is an integer of 1 to 25.)

In addition, the thermosetting silicone rubber composition may further include at least one selected from the group consisting of a heat improver, a flame retardant imparting agent, and a vulcanization recovery inhibitor.

In addition, the heat resistance improver may be a metal oxide or a metal organic acid salt of a transition metal.

According to another aspect of the present invention, there is provided a method of preparing a thermosetting silicone rubber composition, comprising: providing a silicon gum in which a polyorganosiloxane silicone gum is added to a kneader;

A mixing step of mixing by adding a reinforcing silica having a specific surface area of 180 to 240 m 2 / g as a filler and a silicon-based processing aid having a functional group at the kneader;

A dispersion step of stirring and dispersing the resultant mixture of the silicon gum providing step and the mixing step; And adding a at least one surface strength enhancer selected from the group consisting of boric acid compounds and borate compounds to the kneader and dispersing by stirring at elevated temperature or dispersing the surface strength enhancer after stirring at elevated temperature. Characterized in that.

The thermosetting silicone rubber composition according to one aspect of the present invention has improved surface strength, but has excellent working performance in the state of dough in roll dispersing, forming, and cutting processes, and thus requires an extrusion molding having a large diameter or a complicated molding process. Can produce parts In addition, there is an effect that at the same time does not affect the product characteristics after curing.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout the description and claims, unless the context requires otherwise, the word "comprise" is intended to include the stated article, step or group of articles, and steps; It is not meant to exclude an object, step or group of objects or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. In particular, any feature that is indicated to be advantageous or advantageous may be combined with any other feature or feature that is indicated to be advantageous or advantageous.

The thermosetting silicone rubber composition according to one embodiment of the present invention includes a silicon gum, reinforcing silica, a silicon processing aid, and a surface treatment agent.

Composition

1.silicone sword

The polyorganosiloxane silicon gum in this example, preferably has a degree of polymerization of 5,000 to 10,000, a molecular weight of 400,000 to 700,000, and a viscosity of 250,000 centipoise (cPs) to 50,000,000 cPs at 25 ° C. When the viscosity exceeds the above range, it is difficult to disperse the silica, and when the viscosity is below the above range, it is preferable to use a gum having a suitable viscosity because the processability is poor.

The silicon gum used at this time has a repeating unit represented by RaSiO (4-a) / 2. (Wherein R is an aliphatic saturated hydrocarbon group or aliphatic unsaturated hydrocarbon group having 1 to 10 carbon atoms or an aromatic unsaturated hydrocarbon group having 6 to 30 carbon atoms, and a has a value of 1.90 to 2.05)

Specifically, dimethylsilicone gum, methylphenylvinylsilicone gum, methylvinylsilicon gum, hydroxyldimethylsilicone gum, fluorinesilicon gum, etc. can be used, and preferably, methylvinylsilicon having various vinyl contents is added and used.

2. Reinforcing silica

The reinforcing silica has a specific surface area of at least 150 m 2 / g, preferably 180 to 240 m 2 / g, dry silica having an average particle size of 7 to 22 nm, and specific gravity of 1.9 to 2.2 g / cm 3.

Reinforcing silica is preferably 10 to 100 parts by weight, more preferably 20 to 60 parts by weight based on 100 parts by weight of polyorganosiloxane silicone gum. If the amount of the reinforcing silica is less than 10 parts by weight, overall physical property deterioration is likely to occur, and if it exceeds 100 parts by weight, the silica may not be dispersed. As the amount of silica added increases, the surface strength of the product is improved, but the storage property is inferior. 3. Processing aid

The processing aid applies a silicone-based processing aid having a functional group at the end, and plays a role of improving the dispersibility of the filler, preventing crepe hardening, improving flowability, and controlling plasticity. The low viscosity polyorganosiloxane polymer used as the processing aid of this embodiment preferably has a structure of R5Y-SiR1R2 (OSiR3R4) n-YR5. (Wherein R 1, R 2, R 3 and R 4 are each independently any one selected from the group consisting of an alkyl group, a vinyl group and a phenyl group, wherein the alkyl group has 1 to 10 carbon atoms; Y is O, NH or NR 6 ( Wherein R 6 is an alkyl group having 1 to 10 carbon atoms; R 5 is hydrogen or an alkyl group wherein the alkyl group has 1 to 10 carbon atoms and n is an integer of 1 to 25.)

Representative low viscosity polyorganosiloxane polymers are dimethylsilicone, which is a hydroxy group at both ends, methylvinylsilicone polymer, a dimethylsilicone polymer having an alkoxy group at the sock end, and a dimethylsilicone polymer having an amino group at the sock end.

In the present invention, the silicone processing aid as described above is used in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the polyorganosiloxane silicone gum. If the amount of the processing aid is less than 0.5 parts by weight, it is difficult to disperse the reinforcing silica, which is a filler, and if it exceeds 20 parts by weight, stickiness occurs in the composition, resulting in poor workability in a two-roll mill.

4. Surface Strength Enhancer

Surface strength enhancers are used to enhance the surface strength of the product, in this embodiment can be applied to the boric acid compound and borate compound or a mixture of these compounds.

As the boric acid compound, boric acid (CAS # 10043-35-3, H3BO3, Boric Acid, trihydroxido boron) 90% or more may be used, and boric acid having a purity of 99.5% or more in powder form is preferably used.

The borate compound may be triethyl borate (CAS # 150-46-9, C6H15BO3, triethyl borate, triethoxyborane) of 90% or more in liquid form, preferably triethyl borate having a purity of 97.0% or more in liquid form.

These compounds are used individually or in combination of 0.01 to 5 parts by weight based on 100 parts by weight of silicone gum.

5. Other additives

To the silicone rubber composition of the present invention, conventional additives and property improving agents may be further added, if necessary. Examples of the additives include a heat resistance improver, a flame retardant imparting agent, and a vulcanization recovery inhibitor.

As the heat resistance improver, metal oxides or metal organic acid salts of transition metals are used, and the metals include, for example, iron oxide, manganese, nickel, copper, zirconium, cerium, tungsten or titanium. The heat resistance improver prevents oxidation of organic groups, prevents crosslinking between polymers, and breaks the main chain, thereby reducing changes in physical properties such as weight, hardness, tensile strength and elongation among the original rubber properties during heat aging.

The flame retardancy of silicone rubber is different from the flame retardancy of general organic materials, and it is known that the flame retardancy is improved by adding a small amount of platinum compound, because the platinum compound resinizes the silicone rubber. However, when sufficient flame retardancy is not obtained only by the platinum compound, an additional flame retardant imparting agent may be added, and examples thereof include iron oxide, titanium oxide, carbon black, phosphorus compound or nitrogen compound.

As one of the drawbacks of silicone rubber, the vulcanization recovery phenomenon appears under sealing, and in order to improve it, a vulcanization recovery agent is used, for example, an oxygen acceptor such as BaO, CaO, MgO or ZnO. The oxygen acceptor prevents the return of vulcanization by neutralizing the organic acid generated by decomposition of the organic peroxide.

Method of Making Silicone Rubber Composition

Method for producing a silicone rubber composition according to the present invention, silicon gum providing step of injecting a polyorganosiloxane silicon gum into the kneader; A mixing step of adding a reinforcing silica having a specific surface area of 150 m 2 / g or more as a filler and a silicon-based processing aid having a functional group to the kneader; A dispersion step of stirring and dispersing the resultant mixture of the silicon gum providing step and the mixing step; And adding at least one or more surface strength enhancers selected from the group consisting of boric acid compounds and triethyl borate compounds to the kneader and dispersing by stirring at elevated temperature or dispersing the surface strength enhancers after stirring at elevated temperature. It includes.

At this time, the dispersing device for the production of the silicone rubber composition to be used is preferably an open kneader or pressurized kneader, and after initially adding a high-viscosity high viscosity silicone gum and reaching up to 60 ° C. or higher through pre-mixing, reinforcing silica Phosphorus fumed silica and processing aids are divided and added to obtain a silicone rubber composition through final heat dispersion for about 1 to 3 hours at 150 to 180 ° C.

When boric acid is used as the surface strength improving agent, since the melting point of boric acid is 170 ° C., it is preferable that the temperature of the dispersing device is increased to 170 ° C. by adding it before the heat dispersion step.

Uncured Curing of Silicone Rubber Compositions

The silicone rubber composition of the present invention may be cured by adding a vulcanizing agent, and examples of the vulcanizing agent used may include organic peroxides. The organic peroxide forms crosslinks by generating radicals and binding to the vinyl and methyl groups on the silicone polymer chain. Examples of the organic peroxide may be alkyl or acyl. Examples of the organic peroxide include 2,5-dimethyl-2,5-di (t-butylperoxy) hexane or dicumylperoxide. 2,4-dichlorobenzoyl peroxide or benzoyl peroxide. When using an organic peroxide as a vulcanizing agent, it can mix and use 1 or more types of above-mentioned, The content is 0.5-2 weight part with respect to 100 weight part of silicone rubber base compositions. At this time, it is important to disperse the particles evenly and sufficiently using a suitable equipment such as a two roll mill.

After dispersing, the preform is pressurized in a molding mold for 3-7 minutes at 110 ° C to 130 ° C for acyl-based peroxide and for 7-13 minutes at 160-180 ° C for alkyl-based peroxide. After molding, after curing for 4 hours at 180 ℃ to 220 ℃ to remove the decomposed organic peroxide to prevent the phenomenon of hardening degeneration.

Example

Example One

The silicone rubber composition of Example 1 was prepared by the following method. The silicone rubber composition and the process put into the blend are fumed silica (trade name: Reorosil QS-30) with a specific surface area (BET value) of 300 m 2 / g and an average particle size of 16 nm based on 100 parts by weight of methylvinyl silicone polymer. 9 to 11 parts by weight of a hydroxy-terminated polyorganosiloxane low viscosity polymer processing aid having a repeating unit of 2 to 50 parts by weight, dimethyl or methylvinyl siloxy group, and a silicone gum and silica processing aid to the kneader, and then 150 to 180 The mixture was cooled to 100 ° C. after dispersion heating and stirring for 2 hours while maintaining the temperature at 2 ° C. Thereafter, after adding 0.5 parts by weight of boric acid in powder form having a purity of 99.5% or more from Samcheon Chemical Co., Ltd., it was taken out after stirring for 20 minutes.

Example 2

The silicone rubber composition of Example 2 was prepared by the following method. The silicone rubber composition and the process put into the blend are fumed silica (trade name: Reorosil QS-30) with a specific surface area (BET value) of 300 m 2 / g and an average particle size of 16 nm based on 100 parts by weight of methylvinyl silicone polymer. 9 to 11 parts by weight of a hydroxy-terminated polyorganosiloxane low viscosity polymer processing aid having a repeating unit of 2 to 50 parts by weight, dimethyl or methylvinyl siloxy group, and a silicone gum and silica processing aid to the kneader, and then 150 to 180 The mixture was cooled to 100 ° C. after dispersion heating and stirring for 2 hours while maintaining the temperature at 2 ° C. Thereafter, after adding 0.5 parts by weight of triethylborate compound having a purity of 97.0% or more in the liquid form of Tokyo Chemical Industry Co., Ltd., the mixture was stirred for 20 minutes and then taken out.

Comparative example One

The silicone rubber composition of Comparative Example 1 was prepared by the following method. The silicone rubber composition and the process put into the compounding are fumed silica (trade name: Reorosil QS-30) 45 ~ having a specific surface area (BET value) of 300 m ² / g and an average particle size of 16 nm by weight of methylvinyl silicone polymer. 46 parts by weight of a hydroxy-terminated polyorganosiloxane low viscosity polymer processing aid having a repeating unit of 2 to 50 with 9 to 11 parts by weight of a silicone gum and a silica processing aid into a kneader, and then 150 to The mixture was stirred for 2 hours while maintaining the temperature at 180 ° C, and then taken out after cooling to 100 ° C.

Comparative example 2

The silicone rubber composition of Comparative Example 2 was prepared by the following method. The silicone rubber composition and the process put into the blend are fumed silica (trade name: Reorosil QS-30) with a specific surface area (BET value) of 300 m 2 / g and an average particle size of 16 nm based on 100 parts by weight of methylvinyl silicone polymer. 9 to 11 parts by weight of a hydroxy-terminated polyorganosiloxane low viscosity polymer processing aid having a repeating unit of 2 to 50 parts by weight, dimethyl or methylvinyl siloxy group, and a silicone gum and silica processing aid are added to a kneader, and then 80 to 110 ° C. The mixture was stirred for 2 hours while maintaining. Since boric acid in the form of a powder having a purity of 99.5% or more of Samcheon Chemical Co., Ltd., the same as that used in Example 1, after dispersing, stirring and heating at 150 to 180 ° C. for 2 hours, and then taken out after cooling to 100 ° C. .

Comparative example 3

The silicone rubber composition of Comparative Example 3 was prepared by the following method. The silicone rubber composition and the process put into the blend are fumed silica (trade name: Reorosil QS-30) with a specific surface area (BET value) of 300 m 2 / g and an average particle size of 16 nm based on 100 parts by weight of methylvinyl silicone polymer. 9 to 11 parts by weight of a hydroxy-terminated polyorganosiloxane low viscosity polymer processing aid having a repeating unit of 2 to 50 parts by weight, dimethyl or methylvinyl siloxy group, and a silicone gum and silica processing aid to the kneader, and then 150 to 180 The mixture was cooled to 100 ° C. after dispersion heating and stirring for 2 hours while maintaining the temperature at 2 ° C. In Comparative Example 3, 0.5 parts by weight of a fluorine emulsion of TE-3893 product name having a purity of 50.0% from DuPont was added, followed by stirring for 20 minutes.

Examples 1 to 2 and Comparative Examples 1 to 3 are collectively shown in Table 1.

Comparative Example
One Comparative Example
2 Comparative Example
3 Example
One Example
2 Methylvinyl silicone gum
(0.1 to 0.5mol%) 100 100 100 100 100 300㎡ / g Specific Surface Area Fumed
Silica (QS-30) 46.0 46.0 46.0 46.0 46.0 Hosiery Hydroxy
Dimethyl silicone polymer
Degree of polymerization 5 ~ 15 6.3 6.3 6.3 6.3 6.3 Boric Acid, 99.5% Purity - 0.5 - 0.05 - Triethylborate, 97.% purity - - - - 0.5 Teflon emulsion, 50% purity - - 0.5 - -

(Unit: parts by weight)

Experimental Example

Experimental Example 1

After fully plasticizing each of the uncured silicone rubber compositions prepared in Examples and Comparative Examples in a two roll mill, 0.5 parts by weight of organic peroxide (2,5-dimethyl-2) based on 100 parts by weight of the uncured silicone rubber composition , 5-t-butylhexane peroxide 45% paste) was added to disperse sufficiently. Thereafter, the preform subjected to the degassing process was pressed in a molding mold at 170 ° C. for 10 minutes to form a 2 mm thick sheet, and after curing at 200 ° C. for 4 hours in a hot air circulation oven to remove decomposed organic peroxides. In order to prevent the phenomenon of hardening degeneration, the mechanical properties of the sheet were measured according to KS M6518 standard, and the results are shown in Table 2 below.

division Comparative Example
One Comparative Example
2 Comparative Example
3 Example
One Example
2 Plasticity (-) 240 320 280 300 340 Shore A 70 70 70 71 70 Tensile Strength (MPa) 10.5 9.3 10.0 10.4 10.4 Elongation (%) 500 430 480 490 490 Tear strength (N / mm)
Crescent 26 20 25 26 26 importance ( - ) 1.17 1.17 1.17 1.17 1.17 Surface strength usually Great Great Great Great Exterior Good Undispersed
Grains Milky Good Good Shrinkage of Uncured Products none none Has a little none none

As can be seen from the results of Table 2, when comparing Comparative Examples 1 to 3 and Examples 1 to 2, it can be confirmed that the surface strength of Examples 1 to 2 excellent.

In the above description of the thermosetting silicone rubber composition according to the embodiment of the present invention, the present invention is not limited to the above-described embodiments, and those skilled in the art to which the present invention pertains should not depart from the concept of the present invention. Modifications are possible without departing from the scope of the invention.

The scope of the present invention is defined by the following claims, and is not limited to the description of the specification, and all variations and modifications falling within the scope of the claims are included in the scope of the present invention.

Claims

100 parts by weight of silicone gum;
10 to 100 parts by weight of reinforcing silica;
0.5 to 20 parts by weight of a silicon-based processing aid having a functional group at its end;
A thermosetting silicone rubber composition comprising: 0.01 to 5 parts by weight of a surface strength improving agent comprising a mixture of at least one of a boric acid compound and a borate compound.

The method of claim 1,
The boric acid compound is boric acid having a concentration of 90% or more (H3BO3) or boric acid having a purity of 99.5% or more in powder form,
The borate compound is a triethyl borate having a purity of at least 97.0% of the liquid form of the thermosetting silicone rubber composition.

The method of claim 1,
A thermosetting silicone rubber composition having a repeating unit represented by the silicon gum RaSiO (4-a) / 2. (Wherein R is an aliphatic saturated hydrocarbon group or aliphatic unsaturated hydrocarbon group having 1 to 10 carbon atoms or an aromatic unsaturated hydrocarbon group having 6 to 30 carbon atoms, and a has a value of 1.90 to 2.05)

The method of claim 1,
The reinforcing silica has a specific surface area of 180 to 240 m 2 / g, dry silica having an average particle size of 7 to 22 nm, and specific gravity of 1.9 to 2.2 g / cm 3.

The method of claim 1,
The processing aid is a thermosetting silicone rubber composition is a low viscosity polyorganosiloxane polymer having a structure of R5Y-SiR1R2 (OSiR3R4) n-YR5.
Wherein R 1, R 2, R 3 and R 4 are each independently any one selected from the group consisting of an alkyl group, a vinyl group and a phenyl group, wherein the alkyl group has 1 to 10 carbon atoms; Y is O, NH or NR 6, Wherein R 6 is an alkyl group having 1 to 10 carbon atoms; R 5 is hydrogen or an alkyl group wherein the alkyl group has 1 to 10 carbon atoms and n is an integer of 1 to 25.)

The method of claim 1,
The thermosetting silicone rubber composition further comprises at least one or more selected from the group consisting of a heat improver, a flame retardant imparting agent, and a vulcanization recovery inhibitor.

The method according to claim 6,
The heat-resistant improver is a thermosetting silicone rubber composition is a metal oxide or metal organic acid salt of the transition metal.

A silicon gum providing step of introducing a polyorganosiloxane silicon gum into a kneader;
A mixing step of mixing by adding a reinforcing silica having a specific surface area of 180 to 240 m 2 / g as a filler and a silicon-based processing aid having a functional group at the kneader;
A dispersion step of stirring and dispersing the resultant mixture of the silicon gum providing step and the mixing step; And adding a at least one surface strength enhancer selected from the group consisting of boric acid compounds and borate compounds to the kneader and dispersing by stirring at elevated temperature or dispersing the surface strength enhancer after stirring at elevated temperature. Thermosetting silicone rubber composition manufacturing method.