阅读说明：本技术 聚硅氧烷组合物 (Polysiloxane composition ) 是由 聂建 席旻龙 于 2018-04-19 设计创作，主要内容包括：本发明公开了一种无腐蚀性的聚硅氧烷组合物,其可以在室温下固化以形成具有降低模量的弹性体。(A non-corrosive polysiloxane composition that can be cured at room temperature to form an elastomer with a reduced modulus is disclosed.)

1. A polysiloxane composition comprising the following ingredients:

a) a hydroxyl-terminated polyorganosiloxane;

b) a diacetoxysilane having the general formula:

wherein R is₁And R₂Each independently is an alkyl or alkoxy group having one or more carbon atoms;

c) a multifunctional alkoxysilane;

d) a filler; and

e) a catalyst.

2. The polysiloxane composition of claim 1, characterized in that the composition comprises less than 4 parts by weight of the multifunctional acetoxysilane, based on 100 parts by weight of ingredient (a).

3. The polysiloxane composition according to claim 1 or 2, characterized in that component (a) is used in an amount of 10 to 85 wt. -% and component (b) is used in an amount of 0.03 to 1.9 wt. -%, based on the total weight of the starting materials of the polysiloxane composition.

4. The polysiloxane composition according to any one of claims 1 to 3, characterized in that component (b) is used in an amount of from 0.03 to 1.9% by weight and component (c) is used in an amount of from 0.5 to 8% by weight, based on the total weight of the starting materials of the polysiloxane composition.

5. The silicone composition according to any of claims 1 to 4, characterized in that component (a) has a dynamic viscosity at 25 ℃ of 20,000 to 100,000mm²/s。

6. The silicone composition as claimed in any of claims 1 to 5, characterized in that component (b) has the general formula (la), wherein R₁And R₂Each independently is a C1-C16 alkyl group, and the mass ratio of component (a) to component (b) is (75-1400) to 1.

7. Silicone composition according to any of claims 1 to 5, characterised in that component (b) has the general formula, wherein R₁And R₂Each independently an alkoxy group having 1 to 16 carbon atoms, and the mass ratio of the component (a) to the component (b) is (20-1400): 1.

8. The polysiloxane composition according to any one of claims 1 to 7, characterized in that component (d) is used in an amount of from 20 to 60% by weight, based on the total weight of the starting materials of the polysiloxane composition.

9. The polysiloxane composition of any one of claims 1 to 8, characterized in that it may further comprise a silicone resin (f).

10. The silicone composition according to claim 9, characterized in that the dynamic viscosity of component (f) at 25 ℃ is from 10,000 to 500,000 mPa-s.

11. The silicone composition according to any one of claims 1 to 10, characterized in that the composition comprises less than 20 wt.% of plasticizer, based on the total weight of the starting materials of the silicone composition.

12. The polysiloxane composition of any one of claims 1-11, characterized in that the catalyst is an organotin organotitanium.

13. An elastomer, characterized in that it is obtained by curing a polysiloxane composition according to any one of claims 1 to 12.

Technical Field

The present invention relates to a polysiloxane composition, especially a practically non-corrosive polysiloxane composition, which can be cured at room temperature to form an elastomer with a reduced modulus.

Background

Room Temperature Vulcanizing (RTV) silicone rubbers have unique stress-strain characteristics, i.e., low stress, high elongation, low modulus, and are particularly useful for sealing joints between expansion joints and concrete parts of buildings because they can withstand significant deformation caused by temperature, humidity, and stress. Current low modulus RTV silicone rubbers are typically oxime-cured, amide-cured or alkoxy-cured. Basically, their low modulus properties are achieved by the addition of chain extenders or large amounts of plasticizers.

For example, oxime-cured RTV silicone rubbers typically use methyl-or vinyl-bis (methyl ethyl ketoxime) silane as a chain extender, while methyl-or vinyl-tris (methyl ethyl ketoxime) silane as a cross-linker to achieve low modulus; amide-cured RTV silicone rubbers typically use macromolecular chain extenders and crosslinkers having specific structures to achieve low modulus; alkoxy-cured RTV silicone rubbers typically use an ultra-high molecular weight (UHMW) base polymer and a large amount of plasticizer to achieve low modulus.

In theory, the addition of chain extenders causes the molecular chains of the base polymer, typically α, omega-dihydroxypolydimethylsiloxane, to extend linearly upon crosslinking, lowering the crosslinking point, and thereby lowering the modulus.

Currently, low modulus alkoxy-curing RTV silicone rubbers are generally prepared by adding plasticizers, such as methyl silicone oil and α, omega-dimethoxy polydimethylsiloxane, but the plasticizer bleeds out after the silicone composition is cured, thereby contaminating the surrounding substrate.

Disclosure of Invention

In view of the poor mechanical properties and environmental pollution associated with low modulus oxime-cured RTV silicone rubbers, the scarce and expensive starting materials for amide-cured RTV silicone rubbers, and the exudation of added plasticizers in low modulus alkoxy-cured RTV silicone compositions after curing, leading to structural contamination, the present invention provides a substantially non-corrosive silicone composition that can be cured to form reduced modulus elastomers without the need for large amounts of plasticizers.

In a first aspect the present invention provides a polysiloxane composition comprising the following components:

a) a hydroxyl-terminated polyorganosiloxane;

b) a diacetoxysilane having the general formula:

wherein R is₁And R₂Each independently is an alkyl or alkoxy group having one or more carbon atoms;

c) a multifunctional alkoxysilane;

d) a filler; and

e) a catalyst.

Component (a)

According to the invention, component (a) is used as base polymer, which may be any of the various hydroxyl-terminated polyorganosiloxanes conventionally used in the art for the preparation of RTV silicone rubbers or mixtures thereof, typically α, omega-dihydroxypolydimethylsiloxane, which typically has a kinematic viscosity (kinematical viscocity) at 25 ℃ of 1,000 to 350,000mm²S, preferably 20,000 to 100,000mm²And s. As used herein, unless otherwise indicated, the term "kinematic viscosity" is measured according to DIN 51562.

According to the invention, component (a) is generally used in an amount of from 10 to 85% by weight, preferably from 20 to 50% by weight, based on the total weight of the starting materials of the polysiloxane composition.

Component (b)

According to the invention, component (b) is used as a chain extender to increase the molecular chain length of the hydroxyl-terminated polyorganosiloxane.

In the general formula of the component (b), R₁And R₂Each independently of the other is an alkyl group, preferably a C1-C16 alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, isohexyl, tert-hexyl, n-heptyl, isoheptyl and neoheptyl; or an alkoxy group having more than one carbon atom, preferably 1 to 16 carbon atoms, more preferably 2 to 16 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, tert-pentoxy, n-hexoxy, isohexoxy, tert-hexoxy, n-heptoxy, isoheptoxy and neoheptoxy.

The amount of component (b) used varies according to the type of chain extender and is suitably from 0.03 to 1.9% by weight, based on the total weight of the raw materials of the polysiloxane composition, for example 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7% and 1.9% by weight.

In certain embodiments of the invention, component (b) has the general formula (la), wherein R is₁And R₂Each independently is a C1-C16 alkyl group, and the mass ratio of component (a) to component (b) is (75-1400): 1. In other embodiments of the invention, component (b) has the general formula (la), wherein R is₁And R₂Each independently an alkoxy group having 1 to 16 carbon atoms, and the mass ratio of the component (a) to the component (b) is (20-1400): 1.

component (c)

According to the invention, component (c) is used as crosslinker, which can be various polyfunctional alkoxysilane crosslinkers having a functionality of > 3 which are customary in the art for preparing alkoxy-curing RTV silicone rubbers. Examples of suitable multifunctional alkoxysilanes include, but are not limited to, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane.

Component (c) is suitably used in an amount of from 0.5 to 8% by weight, based on the total weight of the starting materials of the polysiloxane composition. For balancing the chain extension and the crosslinking rate, component (b) is suitably used in an amount of from 0.03 to 1.9% by weight, and component (c) is suitably used in an amount of from 0.5 to 5% by weight, based on the total weight of the starting materials of the polysiloxane composition. If the amount of component (c) is less than the corresponding ratio, the silicone composition will cure slowly or not at all, and if it exceeds the ratio, chain extension is ineffective.

Ingredient (d)

According to the present invention, the ingredient (d) may be various fillers conventionally used in the art, such as calcium carbonate (including precipitated calcium carbonate, ground calcium carbonate and activated calcium carbonate), silica, diatomaceous earth, bentonite (such as sodium bentonite and calcium bentonite), kaolin, talc, silica powder, titanium dioxide, alumina, quartz powder and clay minerals, but is not limited thereto.

Ingredient (d) is typically used in an amount of less than 70 wt%, for example 10 to 50 wt%, based on the total weight of the starting materials of the polysiloxane composition. Generally, the higher the filler content in the silicone composition, the more difficult it is to reduce the modulus of the cured elastomer. According to the invention, silicone compositions with high filler contents, typically with filler contents of 20 to 60% by weight, in particular 40 to 60% by weight, can also be cured to form elastomers with a significantly reduced modulus.

Ingredient (e)

The catalyst according to the present invention may be a variety of organotitanium or organotin catalysts conventionally used in the art. Examples of suitable organotitanium catalysts include, but are not limited to, tetra-n-butyl titanate (Tn-BT), tetraisobutyl titanate (Ti-BT), tetra-tert-butyl titanate (Tt-BT), tetraisopropyl titanate (Ti-PT), tetraisooctyl titanate (TOT), diisobutyl bis (acetylacetonate) titanate (DIBAT), diisopropyl bis (acetylacetonate) titanate (DIPAT), bis (ethylacetoacetate) diisopropoxytitanate, bis (ethylacetoacetate) dibutyl titanate. Examples of suitable organotin catalysts include, but are not limited to, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin maleate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin diacetylacetonate, dibutyltin oxide, and dioctyltin oxide.

According to the invention, the amount of component (e) can be specified by the person skilled in the art according to its type and the desired curing speed, and is generally from 0.01% to 5% by weight, based on the total weight of the starting materials of the polysiloxane composition.

Component (f)

According to the present invention, the polysiloxane composition may also comprise a silicone resin (f) to further reduce the modulus of the cured elastomer, which may be any silicone resin known in the art having the general formula:

(M)_a(D)_b(T)_c(Q)_d

wherein M represents a monofunctional siloxane unit R₃SiO_1/2(ii) a D represents a difunctional siloxane unit R₂SiO_2/2(ii) a T represents a trifunctional siloxane unit RSiO_3/2(ii) a Q represents a tetrafunctional siloxane unit SiO_4/2(ii) a a. At least one of b, c and d is not zero.

The silicone resin herein includes any one or combination of structural units M, D, T and Q, and may be, for example, MD, MT, MQ, T, DT and MDT resins, and suitably has a dynamic viscosity at 25 ℃ of less than 500,000 mPa-s, for example, from 10,000 to 500,000 mPa-s.

According to the present invention, the amount of component (f) can be specified as desired by the person skilled in the art, and is generally less than 10% by weight, for example from 1% to 5% by weight, based on the total weight of the starting materials of the polysiloxane composition.

Ingredient (g)

According to the present invention, the polysiloxane composition may provide a reduced modulus without plasticizer (g), but may also include a suitable amount of plasticizer to further reduce the modulus. Examples of suitable plasticizers include, but are not limited to, dimethylsilicone oil having a dynamic viscosity of 10 to 5,000 mPas at 25 ℃ and mineral oil having a dynamic viscosity of 10 to 100 mPas at 25 ℃. Component (g) is suitably used in an amount of less than 20 wt%, for example from 0 wt% to 15 wt%, preferably from 0 to 10 wt%, based on the total weight of the starting materials of the polysiloxane composition.

Other optional ingredients

The polysiloxane compositions of the present invention may also optionally contain other conventional adjuvants and additives such as, but not limited to, UV absorbers (e.g., salicylate, benzotriazole, substituted acrylonitrile, and triazine UV absorbers), and UV stabilizers (e.g., hindered amine ultraviolet light stabilizers).

The polysiloxane compositions of the present invention comprise, based on 100 parts by weight of component (a), less than 4 parts by weight, for example less than 3 parts by weight, less than 2 parts by weight, less than 1 part by weight, less than 0.5 parts by weight, preferably less than 0.1 parts by weight, of a multifunctional acetoxysilane having a functionality of ≧ 3. The polysiloxane composition releases alcohol and acetic acid as by-products during curing. Because acetoxysilanes (including diacetoxysilanes and multifunctional acetoxysilanes) are used in small amounts and the filler in the composition can adsorb the released acetic acid, small amounts, significantly lower than the amount of alcohol released during curing, are released. Thus, the polysiloxane compositions of the present invention still have the advantages of "alkoxy-cured RTV silicone rubbers", are substantially non-corrosive, and are useful as sealants, adhesives or coatings in the building, electronics, electrical and automotive industries.

The silicone composition of the present invention is in one package.

A second aspect of the present invention provides an elastomer obtained by curing the polysiloxane composition according to the first aspect of the present invention.

Detailed Description

The invention is further illustrated by the following examples, without limiting the scope thereof. Any experimental method without the conditions specified in the following examples was selected according to conventional methods and conditions or product specifications.

Inspection method

1. Measurement of Shore A hardness

The Shore A hardness of the cured polysiloxane compositions of the present invention (hereinafter referred to as "elastomers") was determined according to ISO 868-2003 (or Chinese Standard GB/T2411-2008).

2. Measurement of tensile Strength, elongation at Break and 100% modulus

The tensile strength, elongation at break and 100% modulus of the elastomers of the invention were measured according to ISO 37-2011 (or Chinese Standard GB/T528-2009).