JPH08245884A - Low-odor acetoxylated liquid silicone rubber composition - Google Patents

Abstract

PURPOSE: To obtain a low-odor acetoxylated liq. silicone rubber compsn. which diffuses an acetoxylated condensate with a reduced odor into air during curing by compounding specific components. CONSTITUTION: This compsn. contains a hydrotalcite compd. and is prepd. by homogeneously dispersing a curing component and other necessary additives in a polyorganosiloxane base polymer. The base polymer is a polydiorganosiloxane having hydroxyl groups at both molecular ends. The hydrotalcite compd. may be a mixture of hydrotalcite and another hydrotalcite compd., pref. has a specific surface area of 50m<2> / g or higher, and is used in an amt. of 0.1-20wt.% of the compsn. The curing component comprises an acetoxylated silane as the crosslinker and an organotin compd. as the cure catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid silicone rubber composition that undergoes a condensation-type curing reaction, and more specifically, a low-odor acetic acid having reduced odor of a condensation product containing an acetoxy group that diffuses into the air during curing. Mold liquid silicone rubber composition.

[0002]

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION Among the condensation type liquid silicone rubbers, the one-component type is stored in a closed container, and when it is extruded from the container, it reacts with the moisture in the air and the surface The curing begins and progresses to the inside. This curing mechanism is represented by the following formula, which is a condensation reaction between a silanol group-containing polyorganosiloxane that is a base polymer of silicone rubber and a curing agent. -Si-OH + X-Si- → -Si-O-Si- + HX (X: Hydrolyzable organic group such as methoxy, ketoxime, acetoxy) That is, when such a condensation reaction occurs, it is always called HX. In the form, the compound volatilizes into the surrounding environment. The acetic acid type liquid silicone rubber refers to a silicone rubber whose curing agent uses a silicon compound containing an acetoxy group. In such acetic acid type liquid silicone rubber, as a result of the cross-linking reaction, acetoxy group-containing compounds, especially acetic acid represented by CH ₃ COOH, is volatilized in the air, generating a strong acetic acid odor, irritating the eyes and nose, and causing environmental damage. From the point of view, it was not preferable.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an acetic acid type liquid silicone rubber composition having a reduced acetic acid odor.

[0004]

The present inventor has conducted extensive studies to achieve the above object, and as a result, by adding a hydrotalcite compound to an acetic acid type liquid silicone rubber composition, the acetic acid odor during the crosslinking reaction was significantly increased. They have found that they can be reduced, and have completed the present invention. That is, the present invention is a low odor acetic acid type liquid silicone rubber composition containing a hydrotalcite compound.

The low odor acetic acid type liquid silicone rubber composition of the present invention will be described in detail below. The polyorganosiloxane composition, which is the main component of the silicone rubber composition of the present invention, comprises (a) a polyorganosiloxane base polymer, (b) a curing agent, and various additives as necessary, and uniformly mixed. It is dispersed. As the base polymer of the component (a), polydiorganosiloxane having hydroxyl groups at both ends is used. (b) component curing agent,
First, as a cross-linking agent, acetoxy type such as methyltriacetoxysilane and vinyltriacetoxysilane can be mentioned.
When using these, it is not necessary to be limited to one type, and two or more types can be used in combination. Further, among the curing agents of the component (b), as the curing catalyst, iron octoate, cobalt octoate, manganese octoate, tin naphthenate, tin caprylate, tin carboxylic acid metal salts such as tin oleate; dimethyl tin oleate, dimethyl. Organotin compounds such as tin laurate, dibutyltin diacetate, cibutyltin octoate, dibutyltin dilaurate, dibutyltin oleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin methoxide, dibutylbis (triethoxysiloxy) tin, dioctyltin dilaurate are used. To be In the curing agent as the component (b), the amount of the crosslinking agent is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the base polymer as the component (a). If the amount of the cross-linking agent used is less than 0.1 parts by weight, the cured rubber will not have sufficient strength, and if it exceeds 20 parts by weight, the resulting rubber will be brittle, and any of them will not be practically usable. Also, the amount of the curing catalyst blended is (a) the base polymer 1
0.01 to 5 parts by weight is preferable to 00 parts by weight. If the amount is less than this, it is insufficient as a curing catalyst, and it takes a long time to cure, and the curing in the interior far from the contact surface with air becomes poor. On the other hand, if the amount is larger than this, the storage stability will decrease. A more preferable range of the compounding amount is 0.1 to 3 parts by weight.

Next, the hydrotalcite compound which is a characteristic component of the present invention will be described. Hydrotalcite compounds have the general formula: (In the formula, M ²⁺ is Mg ²⁺ , Mn ²⁺ , Fe ²⁺ , CO ²⁺ , Ni ²⁺ , Cu ²⁺ ,
Divalent metals such as Zn ²⁺ , M ³⁺ is Al ³⁺ , Fe ³⁺ , Cr ³⁺ , C
o ^3+, trivalent metal such as In ^3+, A ^n- is ^{OH -, F -, Cl -} , Br
_{^{-, NO 3 -, CO 3}} 2-, SO 4 2-, Fe (CN) 6 3-, CH 3 COO -,
An n-valent anion such as an oxalate ion or a salitate ion is shown, and x is a number satisfying 0 <x ≦ 0.33. ) Is a nonstoichiometric compound. This product is industrially produced by the method described in, for example, U.S. Pat. Nos. 3,539,306 and 3,650,704.

Hydrotalcite has a typical composition formula Mg ₆ Al ₂ (O
H) A natural mineral represented by ₁₆ CO ₃ · 4H ₂ O, which is produced in the Ural region of the former Soviet Union and Sunarum of Norway. Hydrotalcite has a property of capturing anions on the surface. A desirable specific surface area is 50 m ² / g or more, more preferably 100 to 200 m ² / g, the acetic acid odor can be effectively removed. In the present invention, hydrotalcite and a hydrotalcite compound may be used in combination, or two or more hydrotalcite compounds of different types may be used in combination. Further, when there is a concern that the compound of hydrotalcite or the water of crystallization / adsorbed water contained in the hydrotalcite may be affected, the water may be removed in advance by a heating operation, or the compound may be added to the mixture of JP-A No. It is also a preferable method to appropriately mix calcium oxide produced by a wet method as described in No. 186692. The addition amount of these hydrotalcite compounds varies depending on the difference in specific surface area, blending design, type of crosslinking agent used, etc., but as a guide, it is preferably 0.1 to 20 parts by weight per 100 parts by weight of the liquid silicone composition. 0.1
If it is less than 20 parts by weight, the deodorizing ability is lowered, and if it exceeds 20 parts by weight, the effect on the silicone rubber composition cannot be ignored and is not preferred.

The silicone rubber composition of the present invention contains
A filler, a pigment, a heat resistance improver, a flame retardant and the like may be optionally added, and other polyorganosiloxane may be used in combination as long as the effects of the present invention are not impaired. Examples of such substances are usually fumed silica, precipitated silica, reinforcing filler such as diatomaceous earth, titanium oxide, aluminum oxide, zinc oxide, iron oxide, cerium oxide, mica, zinc carbonate, manganese carbonate, Cerium hydroxide, glass beads,
Examples thereof include polydimethylsiloxane and alkenyl group-containing polysiloxane.

[0009]

Embodiments of the present invention will be described below. In addition, all "parts" in the following examples shall show "weight part." Example 1 100 parts by weight of polydimethylsiloxane having both ends of a molecular chain blocked with silanol groups and having a viscosity of 20,000 cP at 25 ° C. was filled with silica powder “R-972” (trade name: manufactured by Nippon Aerosil Co., Ltd.). ) 15 parts, 6 parts of methyltriacetoxysilane as a cross-linking agent, 0.15 parts of dibutyltin dilaurate as a curing catalyst, and Mg ₆ Al ₂ (OH) ₁₆ CO ₃ · 4H ₂ O as a representative composition formula 5 parts of "Kyoward 500" (trade name: manufactured by Kyowa Chemical Industry Co., Ltd.) having a specific surface area of 110 m ² / g were mixed to prepare a silicone rubber composition, which was stored in a cartridge-like sealed container. Before mixing, put "Kyoward 500" in a dryer at 200 ° C for 24 hours.
The adsorbed water was removed before use. Comparative Example 1 A silicone rubber composition prepared in the same manner as in Example 1 except that "Kyoward 500" was not blended was stored in a cartridge-like sealed container. Example 2 Instead of "Kyoward 500", the specific surface area was 12.5 m ² / g
"DHT-4A" (representative composition formula Mg _4.5 Al ₂ (OH) ₁₃ CO ₃
The silicone rubber composition prepared in the same manner as in Example 1 except that 20 parts of 3.5H ₂ O (trade name: manufactured by Kyowa Chemical Industry Co., Ltd.) was used was stored in a cartridge-like sealed container. In addition, "DHT-4A"
Before mixing, the product was placed in a dryer at 200 ° C for 24 hours to remove adsorbed water. These were filled in a Teflon-coated mold having a size of 15 cm × 15 cm and a depth of 2 mm, and the surface was flattened with a spatula to form a square sheet. This sheet is placed on the center floor of a constant-humidity chamber at a constant temperature of 25 ° C and a humidity of 60% in 10 m ³ of each mold, and air is taken into a syringe at a position 30 cm above the sheet at a fixed time and the amount of acetic acid is measured by the headspace gas chromatograph. Was quantified. Table 1 shows the results.

[0010]

[Table 1]

Claims (1)

[Claims] 1. A low odor acetic acid type liquid silicone rubber composition containing a hydrotalcite compound.