WO2012058956A1

WO2012058956A1 - Liquid silicone rubber composition and preparation method therefor

Info

Publication number: WO2012058956A1
Application number: PCT/CN2011/077838
Authority: WO
Inventors: 李彦民
Original assignee: 深圳市森日有机硅材料有限公司
Priority date: 2010-11-01
Filing date: 2011-08-01
Publication date: 2012-05-10
Also published as: CN101983989A; CN101983989B

Abstract

Disclosed are a liquid silicone rubber composition and a preparation method therefor. The liquid silicone rubber composition comprises 100 parts by weight of polydimethylsiloxane terminated with vinyl; 1-400 parts by weight of an inorganic reinforcing agent; 1-20 parts by weight of polydimethylsiloxane having a low viscosity and containing a vinyl on a side chain; 0.01-10 parts by weight of a crosslinking agent; 1-30 parts by weight of polydimethylsiloxane terminated with hydroxyl; and a platinum catalyst for curing the liquid silicone rubber composition. The liquid silicone rubber composition is applicable to an elastomer, a pressure roller, an image heating and fixing device in a copier and a laser printer, and some silicone rubber products.

Description

Liquid silicon rubber compound and preparation method thereof

Technical field

The invention relates to a silicone rubber and a preparation method thereof, in particular to a liquid silicone rubber composition capable of being made into a sponge with high resilience, low pressure and permanent deformation, and a preparation method thereof. Background technique

Silicone rubber has excellent performances such as high temperature resistance, ultraviolet light resistance, radiation resistance, weather resistance, electrical insulation, high gas permeability, physiological inertness, etc., in the aerospace, aerospace, electrical and electronic, light industry, machinery, construction, chemical, medical , 曰 supplies and other aspects have been widely used.

A number of silicone rubber compositions having a compression set which are mainly used for sealing materials, such as containing an alkyl titanate (see European Patent, Patent No. EP 0 581 504 A2), and barium hydroxide (see European Patent, have been disclosed). Patented EP 0 415 180 A2), an organosilicon cation (see European Patent, patent number EP 0 926 190 A1), an addition silicone rubber composition, and an inorganic acid treatment to reduce the acidity of the acidic combination, Thereby, the compression set ratio of the addition-cured silicone rubber composition is improved (see U.S. Patent No. US 2008/0287603 A1). However, these silicone rubber compositions are unstable in compression set, have no good viscosity, and are relatively difficult to store.

Silicone rubber sponge can be obtained by adding a foaming agent to the silicone rubber compound. The composition of the silicone rubber is different to obtain a foamed silicone rubber having different properties. Silicone rubber sponges have the inherent physical properties of silicone rubber and also exhibit improved properties including heat resistance, weather resistance, electrical insulation, flame retardancy, compression set and light weight. They can be used in automotive parts. Such as packaging materials, liners and O-rings, surface coverings for copier rolls, and for a variety of sealing materials. Key factors in the silicone rubber sponge forming process include: effective foaming, uniform microporous structure, smooth surface and non-adhesive surface, and inherent physical properties of the retained silicone rubber.

Many silicone rubber sponge compositions have been disclosed, for example, Japanese Patent Application Publication No. 44-461 (464/11969) and Japanese Patent Application Laid-Open No. Hei 7-247436 (247, 436/1995) are related to a molded type silicone rubber sponge containing a thermally decomposable foaming agent typified by azobisisobutyronitrile. However, the decomposition products produced by the thermally decomposable foaming agent during foaming of these two compositions are harmful to humans, and thus are problematic from the viewpoint of environmental pollution. U.S. Patent (Patent No. US 6096792) relates to 1,1'-azo-di-(1-acetyl) which uses a polymerization degree of 3,000 to 300,000 polyorganosiloxane as a main component and produces a non-toxic gas during foaming. As the blowing agent, without using azobisisobutyronitrile, a silicone rubber sponge composition having a low compression set (180 ° C x 22 hrs) of 8% can be obtained.

The prior art method is to use a thermoplastic resin hollow particle powder which is expanded upon heating (see Japanese Patent Application No. H5-209080 or US Pat. No. 6,300,383) or a pre-expanded thermoplastic resin hollow particle powder (to obtain a low specific gravity silicone rubber composition) as a hair. A foaming agent, formulated with a silicone rubber composition. However, the problem of adding a silicone rubber sponge composition made of a hollow thermoplastic resin is that the cell size is not uniform, and the specific gravity of the foamed silicone rubber varies greatly. On the other hand, when the pre-expanded thermoplastic resin hollow particle powder is used as the foaming agent, it is difficult to mix into the silicone rubber composition, and even if the mixing is successful, there is a problem that the viscosity of the silicone rubber composition after mixing is extremely high. In order to solve these problems, it is also recommended to use paints and plastics containing plastic fine particles treated with liquid substances such as water, solvents or silicone oil (see patent application H4-071664). However, this method is complicated in air spray and will not only be used. The handling of the liquid material is dangerously incorporated into the silicone rubber and has an adverse effect on its properties. The silicone rubber sponge obtained at the same time is composed of a closed gas enthalpy, which makes the rubber sponge have low gas permeability. In some applications (such as a pressure roller), problems may occur, and if the temperature rises, thermal expansion and contraction may occur. Summary of the invention

The technical problem to be solved by the present invention is to provide a liquid silicone rubber composition and a preparation method thereof to solve the problems that the conventional liquid silicone rubber has low resilience and low compression set.

A technical solution to solve the technical problem of the present invention is: Providing a liquid silicone rubber composition, the composition of the liquid silicone rubber composition comprising: 100 parts by mass of a polydimethylsiloxane whose terminal group is a vinyl group; 1 ~ 400 parts by mass of inorganic reinforcing agent; 1 to 20 parts by mass of low viscosity and side group containing vinyl group Methylsiloxane; 0.01 to 10 parts by mass of a crosslinking agent; 1 to 30 parts by mass of a polydimethylsiloxane having a terminal group of a hydroxyl group; a platinum catalyst capable of curing a liquid silicone rubber composition.

As a modification of the present invention, further, 1 to 400 parts by mass of an inorganic reinforcing agent is included. The inorganic reinforcing agent is an untreated silicon powder or a silicon powder whose surface is treated with an organochlorosilane, an organoalkoxysilane, hexamethyldisilazane or an organosiloxane oligomer. While adding the inorganic reinforcing agent, it is also possible to add a semi-reinforcing filler and a non-reinforcing filler in the silicone rubber, such as quartz powder, diatomaceous earth, calcium carbonate, magnesium oxide, silicate 4 bow, mica, alumina. , aluminum hydroxide or carbon black.

As a modification of the present invention, 0.01 to 50 parts by mass of the expansion agent is further included. The expansion agent is a thermoplastic resin hollow particle. The thermoplastic resin includes silicone resin, acrylic resin, and polycarbonate resin.

As a modification of the present invention, 0.01 to 10 parts by mass of a crosslinking agent is further included. The crosslinking agent is an organohydrogenpolysiloxane having at least two Si-H groups in the molecule.

As a modification of the present invention, further, 1 to 20 parts by mass of the surface treatment agent is included. The surface treatment agent is hexamethyldisilazane, dimethyldimethoxysilane or hydroxysilicone oil.

As a modification of the present invention, a heat resistant agent is further included. The heat resistant agent is iron oxide, barium hydroxide or a fatty acid barium salt.

As a modification of the present invention, the platinum catalyst is treated platinum, platinum black, chloroplatinic acid, ethanol modified chloroplatinic acid, chloroplatinic acid/olefin complex, chloroplatinic acid/olefin siloxane complex Or chloroplatinic acid/divinyltetramethyldisiloxane complex.

And, a method of preparing a liquid silicone rubber composition, the method comprising the steps of:

Step 1: 0.1 to 10 parts by mass of a heat resistant agent, 1 to 10 parts by mass of a vinyl-containing polydimethylsiloxane raw rubber, and 0.01 to 10 parts by mass of an inorganic reinforcing agent are uniformly mixed in a kneader Then, 0.01 to 1 part by mass of a surface treatment agent is added for emulsification treatment to obtain a silicone rubber heat-resistant agent capable of reducing compression set;

Step 2: 100 parts by mass of a polysiloxane having a terminal group of vinyl groups, 1 to 400 parts by mass of inorganic Reinforcing agent, 1 ~ 20 parts by mass of surface treatment agent and 1 ~ 10 parts by mass of deionized water are mixed, heat treated for 3 hours, cooled to normal temperature to obtain base rubber; 0.01 ~ 50 parts by mass of expansion agent is added to the In the base rubber, stir and hook, then divide it into first and second aliquots, add 0.01 ~ 1 part by mass of platinum catalyst in the first part and mix well, add 0.01 ~ 10 parts by mass in the second part a crosslinking agent, 0.01 to 10 parts by mass of the heat-resistant agent prepared in the first step, and 0.0001 to 0.01 parts by mass of the inhibitor and mixed;

Step 3: The first and second portions of the second step were mixed and kneaded at 160 ° C for 10 minutes to obtain a foamed liquid silicone rubber composition.

In the method of the present invention, in the second step, the inhibitor is 1-ethynyl-cyclohexanol, 3-methyl-1-penten-3-ol or benzotriazole.

Advantageous technical effects of the present invention are as follows: 1. The present invention uses a low viscosity (viscosity of 200 to 5000 mPa-s at 25 ° C) and a polydimethylsiloxane having a vinyl group in a side chain. This low viscosity polydimethylsiloxane has both good fluidity and adjusts the crosslink density of silicone rubber. And when the expansion agent is mixed therewith, it can be fully expanded and expanded uniformly.

2. The combination of high vinyl content, low viscosity polydimethylsiloxane and polydimethylsiloxane with vinyl group and high viscosity can ensure the fluidity of the glue without affecting the physical machinery. Performance, while adjusting the network cross-link density, improve resilience.

3. Add a cross-linking agent with different hydrogen content through the silicone rubber to find the hydrogen-containing cross-linking agent with the smallest compression set.

4. The use of polydimethylsiloxane whose terminal group is hydroxyl can overcome the large problem of thermal expansion and contraction caused by the excitation change of the fully closed pores of the thermoplastic expansion agent, and the open-cell sponge formed by dehydrogenation can reduce thermal expansion and contraction. Shrink.

5. The iron oxide and barium hydroxide are mixed with the silica powder, and then the raw rubber is made into a heat-resistant agent, and after being emulsified by the surface treatment agent, it plays a good role in reducing compression set. detailed description

The invention provides a platinum-catalyzed liquid silicone rubber composition, which can be made into a sponge, has low viscosity before curing, good fluidity, is suitable for injection molding, and has excellent back after curing. Elasticity and low compression set rate. The polydimethylsiloxane containing a vinyl group in the side chain has good fluidity, and the added expansion agent can be dispersed. The addition of the hydroxyl group-containing polydimethylsiloxane can obtain an open-cell silicone rubber sponge, which is advantageous for reducing the thermal expansion and contraction of the silicone rubber sponge. The silicone rubber sponge having the lowest compression set ratio is obtained by the addition of hydrogen-containing silicone oil having different hydrogen contents. The liquid silicone rubber composition produced by the present invention can be applied to elastomers, pressure rolls and image heating and fixing devices in copying machines and laser printers, as well as some silicone rubber articles which require these properties.

The composition of the liquid silicone rubber composition includes:

Ingredient A: 100 parts by mass of a polydimethylsiloxane whose terminal group is a vinyl group;

Component B: 1 to 20 parts by mass of a polydimethylsiloxane having a low viscosity and having a vinyl group in a pendant group; Component C: 1 to 30 parts by mass of a polydimethylsiloxane having a terminal group of a hydroxyl group;

Ingredient D: 1 to 400 parts by mass of an inorganic reinforcing agent;

Component E: 0.01 to 50 parts by mass of a swelling agent;

Ingredient F: a sufficient amount of platinum catalyst to cure the composition;

Component G: 0.01 to 10 parts by mass of a crosslinking agent;

Component H: 1 to 20 parts by mass of a surface treatment agent;

Ingredient I: 0.1 to 5 parts by mass of a heat resistant agent.

Component A is a polydimethylsiloxane whose terminal group is a vinyl group, and its molecular formula is as shown in (I).

R R R R

R ¹ ― S Ii― a I― o ) _M ^ I―. ) _¾ - S Ii- R ¹

RRR ² R ( J )

m = 400 to 1500, n = 0 to 40 wherein R ¹ is a monovalent aliphatic unsaturated hydrocarbon group, and the monovalent aliphatic unsaturated hydrocarbon group is a vinyl group. R may have the following groups: monovalent alkyl groups such as methyl, ethyl and propyl; alkenyl groups such as vinyl and allyl; cycloalkyl such as cyclohexyl; aralkyl such as β-phenethyl, and aryl such as Phenyl and tolyl; haloalkyl such as 3,3,3-trifluoropropyl and 3-chloropropyl. R ² is methyl, ethyl, propyl, butyl, pentyl, phenyl, vinyl, Any of allyl, 1-butenyl, 1-hexenyl. At 25 °C, the viscosity of component A is between 10,000 and 500,000 mPa's.

Component B is a low viscosity, vinyl group-containing polydimethylsiloxane having a molecular formula of (I):

Wherein R ² is a vinyl group. R ¹ is any ^one of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a phenyl group, a vinyl group, an allyl group, a 1-butenyl group, and a 1-hexenyl group. R may have the following groups: monovalent alkyl groups such as methyl, ethyl and propyl; alkenyl groups such as vinyl and allyl; cycloalkyl such as cyclohexyl; aralkyl such as β-phenethyl, and aryl such as Phenyl and tolyl; haloalkyl such as 3,3,3-trifluoropropyl and 3-chloropropyl. At 25 °C, the viscosity of component B is 200 ~ 5000 mPa's. Because of its low viscosity, good fluidity and adjustable crosslink density, it can mix well with the expansion agent, so that the expansion agent expands completely and expands the cell. Evenly. The amount of the component B added is preferably from 1 to 20 parts by mass based on 100 parts by mass of the component A.

By using a combination of different ratios of vinyl group, high viscosity polydimethylsiloxane component A and high vinyl content and low viscosity polydimethylsiloxane component B, the silicone rubber is ensured. Fluidity does not affect physical and mechanical properties. At the same time, the network crosslink density can be adjusted to improve the rebound resilience.

Component C is a polydimethylsiloxane whose terminal group is a hydroxyl group, and its molecular formula is as shown in (I). Wherein R ¹ is a hydroxyl group. R is an alkyl group, an unsaturated hydrocarbon group or an aromatic group, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group or a pentyl group; an unsaturated hydrocarbon group such as a vinyl group, an allyl group, a 1-butenyl group, or a 1-hexyl group; Alkenyl; cycloalkyl such as cyclohexyl; aralkyl such as β-phenethyl, and aryl such as phenyl and tolyl; haloalkyl such as 3,3,3-trifluoropropyl and 3-chloropropyl. R ² is any one of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a phenyl group, a vinyl group, an allyl group, a 1-butenyl group, and a 1-hexenyl group. The use of polydimethylsiloxane whose terminal group is hydroxyl can overcome the large problem of thermal expansion and contraction caused by the excitation change of the completely closed pore of the thermoplastic expansion agent, and the open-cell sponge formed by dehydrogenation can reduce thermal expansion and contraction. The amount of the component C added is preferably from 1 to 30 parts by mass based on 100 parts by mass of the component hydrazine.

Component D is an inorganic reinforcing agent. The inorganic reinforcing agent may be untreated silicon powder (fumed silica or precipitated silica) or surface organosilane, organoalkoxysilane, hexamethyldisilazane, organosilicon oxide Silicon powder treated with an alkane oligomer or the like. While adding the inorganic reinforcing agent, it is also possible To add a semi-reinforcing filler and a non-reinforcing filler to the silicone rubber, such as quartz powder, diatomaceous earth, calcium carbonate, magnesium oxide, silicate 4 bow, mica, alumina, aluminum hydroxide or carbon black. It is difficult for the excess component D to completely enter the component A, and it is preferable to add 1 to 400 parts by mass of the component D per 100 parts by mass of the component A.

Component E is a swelling agent. The expansion agent is a thermoplastic resin hollow particle. A typical component E is a thermoplastic resin spherical shell to which an inert gas can be attached. The thermoplastic resin includes silicone resin, acrylic resin, and polycarbonate resin. A thermoplastic resin having a softening temperature of 40 to 200 ° C is preferred, preferably 60 to 180 ° C. Inert gases such as air, nitrogen, helium, etc. The average particle size of the component E is from 0.1 to 500 μm, preferably from 1 to 50 μm. Ingredient Ε A solution of a thermoplastic resin can be sprayed into a superheated gas stream by a gas atomizer, and then the solvent is evaporated to granulate the thermoplastic resin. The content of the component E is preferably from 0.01 to 50 parts by mass per 100 parts by mass of the component bis, preferably from 0.1 to 40 parts by mass. When the amount of addition is within this range, the expansion pressure of the expansion agent is sufficient, and it is easy to obtain a uniform size with a moderate size. Hole in the sponge.

Component F is a platinum catalyst. The platinum catalyst may be treated platinum, platinum black, chloroplatinic acid, ethanol modified chloroplatinic acid, chloroplatinic acid/olefin complex, chloroplatinic acid/olefin siloxane complex, chloroplatinic acid/two Vinyl tetramethyldisiloxane complex. Preferably, the mass content of the metal platinum in the component F is 0.1 to 500 ppm. In order to adjust the catalytic activity of the platinum catalyst, some auxiliaries such as 1-ethynyl-cyclohexanol, 3-methyl-1-penten-3-ol or benzotriazole may be added.

Component G is a crosslinking agent. The organohydrogenpolysiloxane containing at least two Si—H groups in the molecule is a crosslinking agent in which an addition reaction of a platinum catalyst and an alkenyl group in the base rubber can be used as a curing agent in an addition reaction. Those known organohydrogenated polysiloxanes which cure silicone rubber compositions. It can be linear, circular or branched. Typically, it has the structural formula (II):

The average composition shown:

R Hy Si 0(4- _x .y)/2 ( Π )

Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group, preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, including alkyl, aryl and aralkyl groups and halogens and cyano groups thereof Substituted form, and preferably free of aliphatic unsaturated bonds; X and y are 1 X 2.2, 0.002 y 1 and 1.002 A positive number of x+y 3. In the molecule, preferably at least two, preferably at least three, SiH groups are present and may be located at the end of the molecular chain or at any intermediate position. The organopolysiloxane containing a Si—H bond may be a trimethylsiloxy-terminated methylhydrogenpolysiloxane, a trimethylsiloxy-terminated methylhydrogensiloxane, and a dimethylsilicone. A polymer of oxyalkylene, a polymer of dimethylhydrosilyloxy-terminated methylhydrogensiloxane and dimethylsiloxane, tetramethyltetrahydrocyclotetrasiloxane or the like.

The organohydrogenated polysiloxane preferably has a viscosity equal to or lower than 300 mPa-s at 25 ° C, and 0.01 to 10 parts by mass of the component G (organic hydrogenation) with respect to 100 parts by mass of the component A (organopolysiloxane). Polysiloxane) is mixed in. Preferably, the organohydrogenpolysiloxane is used in an amount such that each of the alkenyl groups in the component A obtains from 0.05 to 10, more preferably from 1 to 4 silicon-bonded hydrogen atoms. If the number of hydrogen atoms in the silicon is less than 0.05, the crosslinking may be insufficient and satisfactory mechanical strength may not be obtained. If the number of hydrogen atoms is more than 10, the cured product may have poor physical properties, particularly heat resistance and compression set. Further, it is also preferred to add a known platinum catalyst inhibitor such as a polymethylvinylsiloxane cyclic compound, an acetylenic alcohol, and a peroxide to the silicone rubber composition.

Component H is a surface treatment agent. The surface treatment agent may be hexamethyldisilazane, dimethyldimethoxysilane or hydroxysilicone oil. The surface of the reinforcing filler generally contains an active Si—OH group, and the active Si—OH group acts on the Si— 0 or the terminal Si—OH of the silicone rubber molecule to form a hydrogen bond, which causes physical adsorption and chemical bonding, which makes the reinforcing filler It is difficult to disperse evenly in the silicone rubber compound, and the rubber compound will gradually harden during the storage process, the plasticity is reduced, the structure phenomenon occurs, and the refining and processing performance are gradually lost. In order to prevent the structuring of the silicone rubber compound, a structuring agent may be added to deactivate the Si-OH on the surface of the reinforcing filler to improve the affinity between the reinforcing filler and the silicone rubber molecule. , Control physical adsorption and chemical bonding, inhibit the formation of hydrogen bonds, thereby achieving the purpose of preventing structuring. 1 to 20 parts by mass of component H (surface treatment agent) is added to 100 parts by mass of component A (organopolysiloxane).

Ingredient I is a heat resistant agent. The heat-resistant agents added to the silicone rubber are generally iron oxide, barium hydroxide, and fatty acid barium salts. Since the heat-resistant agent has a special complexing effect on Si, it can increase the crosslink density of the silicone material and the stability between the molecular chains, so that the heat resistance, strength, tear resistance and wear resistance of the material are obtained. Greatly improved, and has the function of absorbing and shielding ultraviolet radiation, making the product more resistant to aging. Generally, the heat-resistant agent is prepared by mixing the heat-resistant agent particles with the raw rubber and treating it with a surface modifier. The smaller the particle size, the easier it is to uniformly disperse in the raw rubber. The heat-resistant agent is added in an amount of 0.1 to 5 parts by mass relative to 100 parts by mass of the raw rubber.

The composition of the present invention contains the above-mentioned component A, component B, component F and the like. Preferably, some other additives may be added to the silicone rubber composition. These additives may be flame retardants such as manganese carbonate, zinc carbonate, fumed titanium dioxide, pigments such as iron oxide red, titanium dioxide, carbon black, silicone oils such as dimethyl silicone oil, methylphenyl silicone oil and the like.

The composition of the present invention is produced by mixing the above-mentioned liquid silicone rubber-based ingredients consisting of ingredient A and ingredient B. When heated and cured by the addition of a swelling agent, the composition of the present invention becomes a foamed silicone rubber, and the heating temperature used herein is usually at least 100 ° C, and the preferred temperature range is from 100 ° C to 180 ° C. When the expansion agent is pre-expanded, the heating temperature is preferably in the range of 100 ° C to 180 ° C. The apparatus for producing the silicone rubber composition of the present invention may be various mixers for producing a silicone rubber composition such as a kneader mixer, a pressure kneader mixer, a continuous kneading extruder and the like.

The invention also provides a preparation method of a liquid silicone rubber composition, the preparation method comprising the following steps:

Step 1: 0.1 to 10 parts by mass of heat-resistant agent, 1 to 10 parts of vinyl-containing polydimethylsiloxane raw rubber (viscosity of 10,000,000 mPa-s), 0.01 to 10 parts of inorganic The reinforcing agent is uniformly mixed in the kneader, and then 0.01 to 1 part of the surface treatment agent is added for emulsification treatment, thereby obtaining a silicone rubber heat-resistant agent capable of reducing compression set;

Step 2: 100 parts by mass of a vinyl group having a terminal group of vinyl groups, 1 to 400 parts of an inorganic reinforcing agent, 1 to 20 parts of a surface treating agent, and 1 to 10 parts of deionized water. Mixing, heat treatment for 3 hours, cooling to room temperature, to obtain a base rubber, adding 0.01 to 50 parts of a swelling agent to the base rubber, stirring uniformly, and then dividing it into first and second aliquots, the first one Add 0.01 ~ 1 part of platinum catalyst and mix well, add 0.01 - 10 parts of cross-linking agent, 0.01 - 10 parts of heat-resistant agent prepared in step 1 and 0.0001 ~ 0.01 parts of inhibitor in the second part and mix; Step 3: The first and second portions of the second step were mixed and kneaded at 160 ° C for 10 minutes to obtain a foamed liquid silicone rubber composition.

The invention has the following advantages:

1. The present invention uses a low viscosity (viscosity of 200 to 5000 mPa-s at 25 ° C) and a polydimethylsiloxane having a vinyl group in its side chain. This low viscosity polydimethylsiloxane has both good fluidity and adjusts the crosslink density of silicone rubber. And when the expansion agent is mixed therewith, it can be fully expanded and expanded uniformly.

5. The iron oxide and barium hydroxide are mixed with the silica powder, and then the raw rubber is made into a heat-resistant agent, and after being emulsified by the surface treatment agent, it plays a good role in reducing compression set.

Therefore, the silicone rubber of the present invention is a platinum-catalyzed two-component liquid silicone rubber composition which has low viscosity before solidification and good fluidity, is suitable for injection molding, and has excellent resilience and low compression deformation rate after curing. Therefore, the silicone rubber of the present invention can be used as a product to help meet the needs of applications such as heat insulating gaskets, heat insulating sealants, heat insulating adhesives, printing rollers for printers, or copying machines. Roller, etc.

The invention will now be further described in connection with a number of specific embodiments. In these examples, "parts" means "parts by mass", the viscosity is a value measured at 25 ° C, and the hardness is a value measured by a Shore C hardness meter, which is cured by a flatbed machine during curing.

Related Examples 1

Drying unexpanded expansion agent (AKzo Expand cell 45DU) in a furnace at 90 °C 1 small Time (h). After cooling, 20 parts of a polysiloxane containing 0.2% vinyl (end group is vinyl) and 5 parts of expansion agent were uniformly mixed, and placed in an oven at 150 for 1 h to obtain pre-expansion. A uniform expansion agent. Related Embodiment 2

0.5 parts of iron oxide and 0.5 parts of barium hydroxide (Rodia Chemical O 105 ), 2 parts of vinyl-containing polydimethylsiloxane gum (viscosity of 10,000,000 mPa-s) and 0.4 parts of gas phase white carbon Black (Wacker Chemical N20) is mixed in the kneading machine. Then, 0.2 part of hexamethyldisilazane was added and emulsified to obtain a silicone rubber heat-resistant agent capable of reducing compression set.

Example 1

100 parts of polysiloxane having a terminal group of vinyl groups (viscosity of 20,000 mPa-s), 20 parts of fumed silica having a specific surface area of 200 m ² /g (Wacker Chemical N20), hexamethyldisilazane 6 parts, 3 parts of deionized water, sequentially added materials in a kneader, heated to 140 ° C, heat treated for 3 h. Cold to normal temperature, the base rubber I was obtained. Then, 5 parts of the unexpanded expansion agent (AKZO Expand cell 45DU) was added to the base rubber I, and the mixture was stirred in a kneading machine. Then divide it into two equal parts, A and B. A part of platinum catalyst (square Silicone CA28, platinum content 2000 ppm) was added to part A and mixed, and a hydrogen-containing silicone oil (hydrogen content of 0.75 wt%) of 1.5 parts was added to the B part, and the heat resistance of the related example 2 was added. Adding 0.65 parts of the agent and 0.001 part of the inhibitor to the B part, adding 3 parts of hydrogen-containing silicone oil (hydrogen content of 0.75 wt%) and 0.001 parts of the inhibitor and mixing, and measuring the viscosity of the part A is 100×10 ⁴ mPa′s, B part The viscosity is 98 < 10 ⁴ mPa's and the fluidity is poor. Finally, the mixture of Part A and Part B was mixed and cured at 160 ° C for 10 minutes (min ) to obtain a closed-cell silicone rubber sponge with uneven foaming. The foaming ratio of the foaming agent was 1.2 times, and the obtained silicon was obtained. Poor rubber elasticity. Its performance is listed in Table 1.

Table 1 Compression set

Specific gravity rebound rate [%] Asker C hardness

(180 ° C 22 hrs) [%]

0.72 28 38 55 Example 2

The base rubber was prepared in the same manner as in the base rubber I of Example 1. Then, the pre-expanded expansion agent prepared in the relevant Example 1 was mixed with the base rubber I in a kneader to obtain a liquid silicone rubber base rubber II. The gum base II is then divided into two equal parts, A and B. A part of platinum catalyst (square Silicone CA28, platinum content 2000 ppm) was added to Part A and mixed, and a hydrogen-containing silicone oil (hydrogen content of 0.75 wt%) of 1.5 parts was added to Part B, and the heat resistance of Example 2 was added. 0.65 parts of the agent and 0.001 parts of the inhibitor were mixed. A viscosity measured as parts 20x l0 ⁴ mPa-s, B parts of a viscosity of 19 <10 ⁴ mPa's, relatively good flowability. Finally, the A and B parts were uniformly mixed and cured at 160 ° C for 10 min to obtain a foamed uniform closed-cell silicone rubber sponge. The foamed silicone rubber was observed, and it was found that the foaming ratio of the foaming agent was 2.5 times. The silicone rubber sponge was subjected to a thermal expansion test to obtain a coefficient of expansion of 1.7%, and its properties are shown in Table 2.

Table 2 Example 2 Example 3 Example 4 Example 5 Specific gravity 0.41 0.40 0.40 0.42

Compression set

20.5 15.2 14.6

(180 ° C 22 hrs) [%]

Rebound rate [%] 65 50 55 63

Asker C hardness 30 25 27 33 Example 3

In the same manner as the preparation of the silicone rubber of Example 2, except that the base rubber II was divided into two equal parts A and B, 5 parts of hydrogen-containing silicone oil having a hydrogen content of 0.25 wt% was added to the B portion. The properties of the closed-cell silicone rubber sponge having a uniform foaming are shown in Table 2. Example 4

In the same manner as in the production method of Example 2, except that the base rubber II was divided into two equal parts of A and B, 4 parts of hydrogen-containing silicone oil having a hydrogen content of 0.5 wt% was added to the B portion. The properties of the closed cell silicone rubber sponge having a uniform foaming are shown in Table 2. Example 5

Same as the preparation method of Example 2, except that the base rubber II is divided into two parts of A and B, and then B parts. Two parts of a hydrogen-containing silicone oil having a hydrogen content of 1.00% by weight were added. The properties of the closed cell silicone rubber sponge which obtained uniform foaming are shown in Table 2. Example 6

100 parts of polysiloxane having a viscosity of 20,000 mPa-s, vinyl group of terminal group, 20 parts of fumed silica having a specific surface area of 200 m ² /g (Wacker Chemical N20), 6 parts of hexamethyldisilazane 2 parts of hydroxy-terminated polydimethylsiloxane and 3 parts of deionized water were added to the materials in turn, heated to 140 ° C, and heat treated for 3 h. Cold to normal temperature, the base rubber I was obtained. Then, the pre-expanded expansion agent prepared in the relevant Example 1 was mixed with the base rubber I in a kneader to obtain a liquid silicone rubber base rubber II. The gum base II is then divided into two equal parts, A and B. A part of platinum was added to a portion of the platinum catalyst (Shenri company CA28 platinum content 2000 ppm) 0.6 parts and mixed. To the B portion, 1.5 parts of a hydrogen-containing silicone oil (hydrogen content: 0.75 wt%), 0.65 parts of a heat-resistant agent according to Example 2, and 0.001 parts of an inhibitor were added and mixed. A viscosity measured as parts 20xl0 ⁴ mPa-s, B parts of a viscosity 19xl0 ⁴ mPa- S o Finally, the parts A and B were mixed uniformly, cured for 10 min at 160 ° C, to obtain a uniform foamed openings A silicone rubber sponge uniformly distributed with closed cells. It is observed that the hydrogen produced by the addition of a small amount of hydroxy-terminated polydimethylsiloxane forms open pores. The foamed silicone rubber was cut into thin slices and the surface of the slice was observed under a microscope, and the pore size of the silicone rubber sponge was between 50 μm and 60 μm, and the ratio between the open and closed cells was 1:9. The thermal expansion test was carried out to obtain a coefficient of expansion of 0.5%, and the properties thereof are shown in Table 3.

table 3

Compression set

Specific gravity rebound rate [%] Asker C hardness

(180 ° C 22 hrs) [%]

0.41 8 65 30

As apparent from the above, in the silicone rubber sponge composition of the present invention, when the hydrogen content of the component G is 0.75%, a closed-cell silicone rubber sponge having a small compression set can be obtained. Adding hydroxy-terminated polydimethylsiloxane can obtain a silicone rubber sponge with a small expansion coefficient and a minimum compression set, and the silicone rubber sponge can reduce the shrinkage due to thermal expansion and contraction when used. The deformation caused.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A liquid silicone rubber composition, characterized in that the composition of the liquid silicone rubber composition comprises: 100 parts by mass of a polydimethylsiloxane whose terminal group is a vinyl group; and a viscosity of 1 to 20 parts by mass 200 to 5000 mPa-s and a vinyl group-containing polydimethylsiloxane; 0.01 to 10 parts by mass of a crosslinking agent; 1 to 30 parts by mass of a hydroxyl group-containing polydimethylsiloxane; A platinum catalyst capable of curing a liquid silicone rubber composition.

The liquid silicone rubber composition according to claim 1, which further comprises 1 to 400 parts by mass of an inorganic reinforcing agent.

The liquid silicone rubber composition according to claim 2, wherein the inorganic reinforcing agent is untreated silicon powder or organochlorosilane for surface, organoalkoxysilane, hexamethyldisiloxane Azaxane, organosiloxane oligomer treated silicon powder.

The liquid silicone rubber composition according to claim 1, which further comprises 0.01 to 50 parts by mass of a swelling agent.

The liquid silicone rubber composition according to claim 4, wherein the expansion agent is a thermoplastic resin hollow particle.

The liquid silicone rubber composition according to claim 5, wherein the thermoplastic resin comprises a silicone resin, an acrylic resin, and a polycarbonate resin.

The liquid silicone rubber composition according to claim 1, wherein the crosslinking agent is an organohydrogenpolysiloxane having at least two Si-H groups in the molecule.

The liquid silicone rubber composition according to claim 1, further comprising 1 to 20 parts by mass of a surface treating agent.

The liquid silicone rubber composition according to claim 8, wherein the surface treatment agent is hexamethyldisilazane, dimethyldimethoxysilane or hydroxysilicone oil.

The liquid silicone rubber composition according to claim 1, further comprising a heat resistant agent.

The liquid silicone rubber composition according to claim 10, wherein the heat resistant agent is iron oxide, barium hydroxide or a fatty acid barium salt.

The liquid silicone rubber composition according to claim 1, wherein the platinum catalyst is treated platinum, platinum black, chloroplatinic acid, ethanol-modified chloroplatinic acid, chloroplatinic acid/olefin network. a compound, a chloroplatinic acid/olefin siloxane complex, or a chloroplatinic acid/divinyltetramethyldisiloxane complex.

13. A method of preparing a liquid silicone rubber composition, characterized in that: the preparation method comprises the following steps:

Step 2: 100 parts by mass of a polysiloxane having a terminal group of vinyl groups, 1 to 400 parts by mass of an inorganic reinforcing agent, 1 to 20 parts by mass of a surface treating agent, and 1 to 10 parts by mass of deionized water. Mixing, heat treatment for 3 hours, cooling to room temperature, to obtain a base rubber; adding 0.01 to 50 parts by mass of a swelling agent to the base rubber, stirring and hooking, and then dividing it into first and second aliquots, first 0.01 to 1 part by mass of a platinum catalyst is added and mixed, and 0.01 to 10 parts by mass of a crosslinking agent, 0.01 to 10 parts by mass of a heat-resistant agent prepared in the first step, and 0.0001 to 0.01 parts by mass are added to the second portion. Inhibitor and mix;

The method for preparing a liquid silicone rubber composition according to claim 13, wherein in the second step, the inhibitor is 1-ethynyl-cyclohexanol or 3-methyl-1- Penten-3-ol or benzotriene ^p .