KR20040076434A - One component room temperature vulcanizable alkoxy sealant composition with improved flowability and mechnical strength - Google Patents

Abstract

PURPOSE: Provided is a one-liquid type alkoxy sealant composition improving a fluidity and mechanical properties, which can be used for sealing, bonding, and protecting electric/electronic parts and terminals. CONSTITUTION: The one-liquid type alkoxy sealant composition contains 100pts.wt. of an organopolysiloxane represented by the formula 1: (OR)2RSiO-(SiR2O)n-R(OR)2, 1.5-8pts.wt. of a crosslinking agent represented by the formula 2: R'nSi(OCH3)4-n, 10-40pts.wt. of a dry or wet silica as a reinforcing filler having a specific surface area of 100-500m2/g, 0.1-5pts.wt. of a silane-based adhesion improving agent, and 0.1-8pts.wt. of a titanium chelate compound selected from a diethanolamine titanium chelate, an acetylacetonate titanium chelate, an ethylacetoacetate titanium chelate, a triethanolamine titanium chelate. In the formula 1, R is methyl and n is an integer of 500-1000. In the formula 2, R' is methyl, ethyl, or vinyl and n is 1 or 2.

Description

One component room temperature vulcanizable alkoxy sealant composition with improved flowability and mechnical strength

The present invention relates to a one-component alkoxy sealant composition having improved flowability and mechanical properties at the same time, and more particularly, by using a titanium chelate compound, it reacts with the hydroxyl group of the reinforcing filler, which causes the flowability, and improves flowability. In addition, the present invention relates to a one-component alkoxy sealant which does not degrade mechanical properties at the same time by allowing a good dispersion.

As is known about the basic composition of one-part silicone rubber, a large amount of silica such as dry or wet silica with a large specific surface area is generally added to improve the high mechanical properties of the rubber after curing. However, if a large amount of silica is added to reinforce the mechanical strength, this rubber base composition adversely affects the flowability.

The following studies have been reported to solve the problem of deteriorating the flow on the composition.

(1) U.S. Patent No. 5,506,303 solves the above problem by mixing a surface treating agent (Silane or silazane compound) with water and then heating and cooling, but in this process, organopolysiloxane and wet or dry silica are mixed. When the surface of silica is added with additives and water, the silicone rubber composition has flow characteristics but the dispersion of silica is not good, resulting in fine silica dispersion (lower physical properties due to the influence of silica fine dispersion during specimen fabrication after curing). Has characteristics.

(2) US Pat. No. 5,352,724 discloses a process of adding water after mixing organic tetraethyl titanate (TET) with a surface treating agent (Silane or silazane compound), and using a dry or wet silica of 15% or less. Although excellent in properties, the mechanical strength is inferior, and storage stability and flowability are inferior when using more than 15% of silica. In addition, when using natural silica having a particle size of 10 μm or more, the problem of silica fine dispersion in the sheet after curing is solved, but the mechanical properties are low due to the use of natural silica having no reinforcing properties.

When the process of (1) and (2) is applied to the basic composition of the one-component alkoxy sealant, a problem of gelation may occur during the process, and when the process of (2) is applied to the basic composition, the amount of silica is 15% or less. Only when mixed, it exhibits flowability and storage stability and cannot produce satisfactory effects in reinforcement, resulting in a drop in mechanical strength of tensile and tear.

Accordingly, the present inventors have made a composition of a one-component alkoxy sealant using a reinforcing filler in an appropriate content to improve the flowability as well as to not lower the mechanical properties including strength, and the flowability using a titanium chelate compound It reacts with the hydroxyl group of the reinforcing filler, which is a cause to prevent the flow, and improves the flowability, thereby allowing the increase of the reinforcing filler in the formulation, and acting as a catalyst in the curing reaction of the sealant and participating in the reaction as a crosslinking agent, The present invention has been completed by developing a one-component alkoxy sealant that does not drop off.

Accordingly, an object of the present invention is to provide a one-component alkoxy sealant composition having both flowability and mechanical properties.

The present invention is based on 100 parts by weight of organopolysiloxane containing at least two alkoxy groups, 1.5 to 8 parts by weight of crosslinking agent, 10 to 40 parts by weight of dry or wet silica having a specific surface area of 100 to 500 m ² / g as a reinforcing filler. And a one-component alkoxy sealant composition containing 0.1 to 5 parts by weight of an adhesion promoter and 0.1 to 8 parts by weight of a titanium chelate compound.

Referring to the present invention in more detail as follows.

The present invention uses a titanium chelate compound to react with the hydroxyl group of the reinforcing filler, which is the cause of impeding the flowability, to improve the flowability to enable the increase of the reinforcing filler in the formulation, and to serve as a catalyst in the curing reaction of the sealant. In addition, the present invention relates to a one-component alkoxy sealant that does not degrade the mechanical properties by participating in the reaction as a crosslinking agent.

The organopolysiloxane used in the present invention is a compound represented by the following formula (1) containing at least two alkoxy groups, and has a viscosity of 5000 to 20,000 cP. Curing advances by the crosslinking reaction of the silane containing a Si-OR group.

(OR) ₂ RSiO- (SiR ₂ O) _n -SiR (OR) ₂

In Chemical Formula 1; R is a methyl group and n is an integer of 500-1000;

At this time, if the viscosity of the siloxane is less than 5000 cP, the mechanical properties of the sealant is weak, and if it exceeds 20000 cP, the viscosity of the subject is so high that the final viscosity of the sealant is high, causing workability problems.

The crosslinking agent used in the present invention is a compound represented by the following Formula 2, and serves to crosslink the sealant by reacting with the organopolysiloxane.

R ' _n Si (OR) _4-n

In Chemical Formula 2; R is a methyl group or an ethyl group, R 'is a methyl group, an ethyl group, or a vinyl group, n is 1 or 2.

Content of such a crosslinking agent is 1.5-8.0 weight part with respect to 100 weight part of said organopolysiloxane, More preferably, it is 2.0-7.0 weight part. In this case, when the content is out of the above range, there is a problem in that the curing of the sealant is poor and a rubber phase is not formed or the curing speed is too slow.

In addition, as the reinforcing filler used in the present invention, it is preferable to use dry or wet silica having a specific surface area of 100 to 500 m ² / g, and more preferably fumed having specific surface areas of 150, 200, and 380 m ² / g. In the case of using silica with specific surface area less than 100 m ² / g, when the sealant is manufactured, it is insufficient in reinforcement property and weak in physical properties, and when it exceeds 500 m ² / g, it is mixed in the mixer due to high viscosity. This is an impossible problem.

The surface of the reinforcing filler contains a hydroxyl group called silanol group (Si-OH). That is, since they contain water, they have hydrophilic properties. Therefore, in order to solve stability and flow problems during storage of hydrophilic silica, hydrophilic surfaces are hydrophobically modified through coupling agents or chemical processes. Hydrophobic silica is also used. However, even when hydrophobic silica such as Aerosil R972 or Aerosil R812 (Degussa) is applied to a silicone sealant requiring flowability and storage stability, it can be used only after surface treatment. However, R-8200 can be used without the surface treatment agent treatment process.

The reinforcing filler is used in order to have excellent flowability with reinforcing properties, and the content is preferably 10 to 40 parts by weight, more preferably 15 to 20 parts by weight based on 100 parts by weight of the organopolysiloxane. In this case, when the content is less than 10 parts by weight, there is a problem in that the mechanical properties are weak due to lack of reinforcement, and when the content exceeds 40 parts by weight, the viscosity is increased and it is impossible to mix.

Adhesion promoters for enhancing the self-adhesion of the sealant include amino silanes such as γ -aminopropyltriethoxysilane and N- (aminoethyl) -γ -aminopropyltrimethoxysilane and γ -glycidoxy Epoxysilanes, such as propyl trimethoxysilane and (beta)-(3, 4- epoxycyclohexyl) ethyl trimethoxysilane, and gamma- mercaptopropyl trimethoxysilane etc. are preferable. As for content of an adhesion promoter, 0.1-5.0 weight part is preferable with respect to 100 weight part of said organopolysiloxane, and 0.3-0.6 weight part is more preferable. In this case, when the content is less than 0.1 part by weight, it is difficult to expect the improvement of the self-adhesive force of the sealant. When the content exceeds 5.0 parts by weight, the viscosity increases during the compounding and storage of the sealant, resulting in poor workability.

In addition, in the production of one-component alkoxy sealants, titanium chelate compounds are used as a surface treating agent of silica and as a crosslinking catalyst. These titanium chelate compounds are selected from diethanolamine titanium chelate, acetylacetonate titanium chelate, ethylacetoacetate titanium chelate, and triethanolamine titanium chelate. Can be used 0.1-8.0 weight part is preferable with respect to 100 weight part of said organopolysiloxane, and, as for content of the said titanium chelate compound, 0.5-1.3 weight part is more preferable. At this time, when the content is less than 0.1 parts by weight, there is a problem that the curing speed is too slow or uncured, and when the content is more than 8.0 parts by weight, the curing speed is too fast, resulting in poor workability.

By using such a titanium chelate compound, a resin is cross-linked to form a resin by transesterification with a hydrogen atom of a hydroxyl group of a silanol (Si-OH) group of a reinforcing filler, which is a cause of impeding flowability, or of a silica Surface treatment.

(OR) _n Ti (X) _4-n + OH-Si ~~~ ↔ (X) _4-n Ti (OR) _n-1 -O-Si ~~~ + ROH

In Scheme 1, R is an alkyl group having 1 to 4 carbon atoms, and X is a functional group containing oxygen or nitrogen atoms capable of forming coordinating bonds with titanium, and oxygen or nitrogen atoms are coordinated with titanium to form a chelate compound. . Examples of functional groups capable of forming coordination bonds with titanium include N (CH ₂ CH ₂ O) ₂ = (n = 2), -OCCH ₃ = CHCOCH ₃ (n = 2), -OCCH ₃ = CHCOOC ₂ H ₅ (n = 2), N (CH ₂ CH ₂ O) ₂ ≡ (n = 1) and the like can be used.

When an extra titanium chelate compound is present after such surface treatment, the titanium chelate compound is hydrolyzed with water in the air to form a hydroxyl group, and the hydroxyl group crosslinks with the alkoxy group of the crosslinking agent and the polymer. Since the hydrolysis reaction of the alkoxy group of the titanium chelate compound is faster than the hydrolysis reaction of the crosslinking agent, the titanium chelate compound acts as a catalyst of the sealant.

The one-component alkoxy sealant manufactured with the composition described above has good flowability and does not deteriorate in mechanical properties, so that it is used in the electronics, electrical, automotive, mechanical industries and construction fields for the use of potting materials for adhesives, sealing materials and parts protection. It is expected to be very useful.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.

Example 1

100 parts by weight of 5,000 cp of dimethylpolysiloxane having two methoxy groups and one methyl group substituted at the end, 2.5 parts by weight of methyltrimethoxy silane and 1.0 part by weight of dimethyldimethoxysilane as a crosslinking agent, and a specific surface area of 200 as a reinforcing filler. 17 parts by weight of m ² / g of hydrophilic fumed silica (Aerosil 200, Degussa) were divided and dispersed in a mixer for 15 minutes. At the time of dispersion, the inside of the mixer is decompressed to a vacuum to prevent the mixing of moisture in the air with the compound.

0.8 parts by weight of the acetylacetonate titanium chelate compound is added to the compound in which silica is dispersed, and mixed so that the hydrophilic groups on the surface of the silica are treated with the titanium chelate compound.

The addition of the titanium chelate compound should be performed after all the dispersion of the silica is finished to increase the dispersing power and obtain the desired flowability. After the defoaming step, 0.3 parts by weight of γ -glycidoxypropyltrimethoxysilane was added as an adhesion promoter, and a sealant was manufactured by a reduced pressure stirring process.

Example 2

In Example 1, the amount of methyltrimethoxysilane was increased to 3.5 parts by weight, and no dimethyldimethoxysilane was added.

Example 3

In Example 1, methyltrimethoxysilane was not added, and 2.0 parts by weight of vinyltrimethoxysilane was added.

Example 4

In Example 1, the amount of methyltrimethoxysilane was reduced to 2.0 parts by weight, and the amount of acetylacetonate titanium chelate compound was increased to 1.5 parts by weight.

Comparative Example 1

In Example 1, the addition amount of the acetylacetonate titanium chelate compound was increased to 15.0 parts by weight.

Comparative Example 2

In Example 1, the amount of methyltrimethoxysilane was increased to 3.5 parts by weight, dimethyldimethoxysilane was not added, and 2.0 parts by weight of vinyltrimethoxysilane was added. 2.0 parts by weight of DBTDA (Dibutyltindiacetate) was added as a curing catalyst without adding the acetylacetonate chelate compound.

Test Example

The sealants prepared in Examples and Comparative Examples were packaged in a 310 ml cartridge made of PE and stored in a constant temperature and humidity room for 24 hours, and then measured mechanical properties, flowability, and the like.

The specimens were cured at a thickness of 2 mm for 72 hours in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 50%. The specimens were prepared by KS M 6518, and the physical properties thereof were shown in Table 1 below.

The viscosity of the sealant was measured using a Brookfield viscometer immediately after dispensing, and the flowability of the sealant was measured by the diameter of the sealant spread until the sealant was cured after discharging the sealant through a 5 mm diameter nozzle in a circle of 2 cm diameter in the horizontal plane. Evaluated. For each specimen, four diameters were measured at an angle of 45 degrees, and then the average values were compared to evaluate each flowability. The curing rate was measured at the time of one minute intervals immediately after discharging by applying the SOT method (SkinOver Time).

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Curing time 25 22 23 22 15 28 The tensile strength 35 34 33 36 36 29 Tear strength 15 14 14 15 17 11 Elongation 547 534 530 549 495 487 Hardness 29 29 29 30 31 26 importance 1.05 1.05 1.05 1.06 1.06 1.06 Viscosity (cP) 28040 27500 27000 30000 48000 78000 Flowability (cm) 12.0 11.5 12.0 11.0 4.5 4.0

As shown in Table 2, the sealant prepared by the examples of the various types and composition of the silane according to the present invention has improved flow properties and excellent mechanical properties such as tensile strength, tear strength, and curing, compared to the comparative example. Time was also appropriate.

As described above, the one-component alkoxy sealant according to the present invention uses a reinforcing filler to increase the strength while the titanium chelate compound treats hydrophilic groups on the surface of the reinforcing filler and acts as a curing catalyst, thereby providing good flowability and mechanical properties. The physical properties are also not deteriorated, so it is expected to be very useful in the electronics, electrics, automobiles, machinery industries, and construction fields for sealing, bonding, and protecting electrical and electronic components and terminals.

Claims (3)

Next to 100 parts by weight of the organopolysiloxane represented by the following formula (1), 1.5 to 8 parts by weight of the crosslinking agent represented by the following formula (2), 10 to 40 weight of dry or wet silica having a specific surface area of 100 to 500 m ² / g as a reinforcing filler One part alkoxy sealant composition comprising 0.1 to 5 parts by weight of a silane adhesion promoter and 0.1 to 8 parts by weight of a titanium chelate compound: [Formula 1] (OR) ₂ RSiO- (SiR ₂ O) _n -R (OR) ₂ In Chemical Formula 1; R is a methyl group and n is an integer of 500-1000; [Formula 2] R ' _n Si (OCH ₃ ) _4-n In Chemical Formula 2; R 'is a methyl group, an ethyl group, or a vinyl group, n is 1 or 2. The method of claim 1, wherein the adhesion promoter is γ -amino propyltriethoxysilane, N- (aminoethyl) -γ -aminopropyltrimethoxysilane, γ -glycidoxypropyltrimethoxysilane, β- (3 , 4-epoxycyclohexyl) ethyltrimethoxysilane and γ- mercaptopropyltrimethoxysilane. According to claim 1, wherein the titanium chelate compound is diethanolamine titanium chelate (Diethanolamine titianium chelate), acetylacetonate titanium chelate (Acetylacetonate titianium chelate), ethylacetoacetate titanium chelate (Ethylacetoacetate titianium chelate), triethanolamine titanium chelate (Triethanolamine titanium chelate) titianium chelate), one-component alkoxy sealant composition, characterized in that.