JP2000119524A - Self cross-linkable silicone emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a self-crosslinkable type silicone emulsion having high shelf stability, capable of forming a coating film having toughness and flexibility and excellent adhesivity to a substrate. SOLUTION: A cyclic polysiloxane or a polysiloxane containing a terminal silanol group and/or a terminal alkoxysilyl group (A) is mixed with an organosilicon compound containing a block isocyanate group and an alkoxysilyl group (B) and the mixture is emulsified by water in the presence of a catalyst for promoting a reaction between both the components. The emulsion is applied to a substrate and dried and heat-treated at a temperature to dissociate a blocking agent of the block isocyanate group to form a coating film having fixed performances.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a silicone emulsion which is self-crosslinkable, that is, capable of crosslinking without adding an external crosslinking agent.

[0002]

2. Description of the Related Art Silicone emulsions are
It has a wide range of applications such as release agents, release agents, paints, fiber treatment agents, glass fiber treatment agents, defoamers, and polishing agents. The production of a stable silicone emulsion is achieved by increasing the molecular weight of the reactive siloxane oligomer during emulsification by self-polycondensation (for example, Japanese Patent Publication Nos. 34-2041 and 4-13995).
) Or high molecular weight using a chain extension / crosslinking reaction with a polyfunctional alkoxysilane (for example, JP-B-46-410).
38, Japanese Patent Publication No. 56-38609, etc.). Emulsions of silicones of this high molecular weight are highly stable and provide a flexible dry film. The silicone emulsion partially having silanol groups or alkoxyl groups is self-crosslinked at the same time as drying to give a film having a higher molecular weight.

[0003] However, a silicone film comprising a polysiloxane skeleton has a drawback of poor adhesion and adhesion to a substrate, and although it is rich in flexibility, it does not have sufficient toughness.

[0004] Since isocyanate groups react with active hydrogen groups contained in the surface of a base material (eg, plastics) and chemically bond, it is necessary to introduce an isocyanate group into silicone to improve adhesion to the base material. it can. However, free isocyanate groups react with water to cause decarboxylation and change to amino groups, so that the isocyanate groups introduced into the silicone must be blocked in order to form an emulsion. However, when a silicone having a blocked isocyanate group introduced therein is increased in molecular weight to obtain a stable emulsion, emulsification becomes difficult unless an organic solvent is added to lower the viscosity. The use of an organic solvent is, of course, not preferable because VOC is emitted into the atmosphere.

Accordingly, an object of the present invention is to provide a stable self-crosslinking solvent-free silicone emulsion which forms a film having excellent adhesion to a substrate and having flexibility and toughness.

[0006]

The above object is achieved by the present invention. Therefore, the present invention provides (A) a silicone oligomer selected from a cyclic diorganopolysiloxane or a linear diorganopolysiloxane having a silanol group and / or an alkoxysilyl group at a terminal, and (B) at least one block of each An organosilicon compound having an isocyanate group and an alkoxysilyl group,
Provided is a silicone emulsion obtained by emulsifying by adding water in the presence of a catalyst that promotes the reaction between the component (A) and the component (B).

[0007]

DETAILED DESCRIPTION Component (A) A first class of silicone oligomers that can be used as component (A) is a cyclic dialkylpolysiloxane, especially a cyclic dimethylpolysiloxane, in which a ring is formed by 3 to 10 siloxane bonds, for example, Octamethylcyclotetrasiloxane. The second class is diorganopolysiloxanes terminated at both ends with silanol groups and / or alkoxysilyl, such as dimethylpolysiloxane with silanol groups at both ends or dimethylpolysiloxane with methoxysilyl groups at both ends. A first class of silicone oligomers is preferred.

Component (B) The first class of component (B) includes silane monomers having a blocked isocyanate group and an alkoxysilyl group. This can be obtained by blocking a silane monomer having a free isocyanate group and an alkoxysilyl group, for example, an isocyanate group of γ-isocyanatopropyltrimethoxysilane with a blocking agent. Instead of a silane monomer, a silicone oligomer having an isocyanate group and an alkoxysilyl group blocked with a blocking agent also belongs to this class. For example, γ-blocked by one substituent of the central silicon atom
The silicone oligomer is an isocyanatopropyl group, and the remaining three substituents are terminal alkoxysilyl polydimethylsiloxane chains.

The second class of the component (B) is to block a part of the isocyanate group of the terminal isocyanate compound (urethane prepolymer) having a silicone skeleton in a side chain or a main chain, and to block the remaining isocyanate group and an active hydrogen-containing compound. It is a compound obtained by introducing an alkoxysilyl group by reaction with an alkoxysilane. As is well known, the urethane prepolymer is obtained by reacting a polyol component such as a low molecular weight polyol, a polyether polyol or a polyester polyol with a polyisocyanate compound in an NCO / OH equivalent ratio excess. At this time, a precursor urethane prepolymer is obtained by using a compound containing a silicone skeleton as all or a part of the polyol component. For example, a precursor urethane prepolymer can be obtained by reacting an excess polyisocyanate compound with a polyester polyol produced by a conventional method from a dialkylpolysiloxane oligomer having alcoholic hydroxyl groups at both ends and a dibasic acid.

[0010] Polyisocyanate compounds which can be used are known and include, for example, aromatic diisocyanates such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI) and xylylene diisocyanate (XDI), and hexamethylene diisocyanate (HM).
DI), aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate (IPDI) and 4,4′-dicyclohexylmethane diisocyanate, dimers, trimers and trimethylolpropane of these diisocyanates Polyhydric alcohol adducts can be mentioned.

[0011] Blocking agents and methods of blocking isocyanate groups are also known. Examples are secondary alcohols, tertiary alcohols, active methylene compounds, oximes, lactams, imidazoles and the like. In the reaction with the blocking agent, a catalyst such as an organotin compound or an alkali metal alcoholate can be used.

The component (B) is obtained by applying the emulsion to a substrate, drying it and heating it to 100 to 200 ° C. to dissociate the blocking agent for the isocyanate group, reacting with the component (A) to further increase the molecular weight, It also reacts with active hydrogen groups on the surface of the substrate to help increase the adhesion strength of the coating film to the substrate. A relatively low heating temperature so that the substrate can withstand this heat treatment,
For example, oximes and lactams that dissociate at around 120 ° C. are preferably used as blocking agents.

The emulsified components (A) and (B) contain silanol groups or alkoxysilyl groups which react with each other to form new siloxane bonds, or polysiloxane rings which form new siloxane bonds by hydrolysis. And
Due to the formation of these new siloxane bonds, the components (A) and (B) are polycondensed in the emulsion to increase the molecular weight.

In general, such a polycondensation reaction requires a catalyst such as an acid, a base, and an organometallic compound. In general, an emulsifier is required for emulsification. For this reason, in emulsifying the components (A) and (B) of the present invention, it is preferable to use an emulsifier having a function as a catalyst as all or a part of the emulsifier.

Examples of such emulsifiers include long-chain alkylbenzene sulfonic acids, long-chain alkyl naphthalene sulfonic acids, aliphatic sulfonic acids, silyl alkyl sulfonic acids, and long-chain alkyl-substituted diphenyl ether sulfonic acids as anionic emulsifiers. If long-chain alkylbenzenesulfonic acid is used, dodecylbenzenesulfonic acid is preferred. Further, as a cationic emulsifier, a compound having a long chain alkyl group
Secondary ammonium salts can also be used. An example is
Alkyltrimethylammonium salts such as octadecyltrimethylammonium chloride and hexadecyltrimethylammonium chloride; dialkyldimethylammonium salts such as dioctadecyldimethylammonium chloride, dihexadecyldimethylammonium chloride and didodecyldimethylammonium chloride; and benzalkonium chloride. . These cationic emulsifiers may not have sufficient catalytic activity by themselves depending on the kind thereof. In such a case, it is necessary to use an alkali catalyst such as sodium hydroxide or potassium hydroxide in combination.

In order to promote the hydrolysis or polycondensation reaction, metal organic acid salts such as alkyltin organic acid salts and zinc organic acid salts, organic metal alcoholates such as tetrabutoxytitanium and the like, amines such as n-butylamine and imidazole, etc. A catalyst such as a salt can be used if necessary.

These emulsifiers having a catalytic action may be used in combination with conventional nonionic surfactants, if necessary. Examples are glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkyl ethers,
It includes polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, and polyoxyethylene-polyoxypropylene block copolymers. In general, the emulsified state is improved by the combined use of a nonionic surfactant.

Emulsification can be carried out by adding water in which an emulsifier (catalyst) has been previously dissolved to a mixture of the components (A) and (B), and using an emulsifier such as a homogenizer, a colloid mill, and a line mixer. The ratio of the other components to the (A) component can vary greatly, but generally, as solids, per 100 parts by weight of the (A) component, (B)
Component 1 to 200 parts by weight (preferably 5 to 50 parts by weight),
The emulsifier (catalyst) is 1 to 50 parts by weight (preferably 2 to 20 parts by weight).

According to the present invention, di-, tri- or tetraalkoxysilane can optionally be added to the mixture of component (A) and component (B) prior to emulsification. The component (C) reacts with the component (A) and the component (B) and contributes to increasing the molecular weight of the reaction product. Examples thereof are γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldiethoxysilane, 3-N- (2-aminoethyl) aminopropyltrimethoxysilane, 3-N- ( 2
-Aminoethyl) aminopropyltriethoxysilane,
Aminoalkylalkoxysilanes such as 3-N- (2-aminoethyl) aminopropylmethyldimethoxysilane, and methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, tetramethoxysilane, tetraethoxy Silane, methylvinyldimethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, γ-
Mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane and the like.

The water is suitably used in the same amount to 5 times as the total weight of the components (A) and (B) and, if added, the component (C). The emulsion after emulsification is 50 ~
The mixture is heated under stirring at 90 ° C. for 1 to 10 hours, and after cooling, neutralized with an alkali when an anionic emulsifier is used, and neutralized with an acid when a cationic emulsifier is used in combination with an alkali. Colloidal silica (silica sol) can be added to the thus-obtained silicone emulsion of the present invention. Its purpose is to further improve toughness,
If too much is added, other properties of the dried film are impaired, so the solid content should be kept at 50 parts by weight or less per 100 parts by weight of component (A).

[0021]

EXAMPLES In the following Examples and Comparative Examples, "parts"
And "%" is based on weight.

Synthesis example 1 of component (B) γ-isocyanatopropyltrimethoxysilane 100
To this part, 45 parts of methyl ethyl ketoxime was gradually added under stirring, and the reaction was carried out at a system temperature of 80 ° C. for 60 minutes. After confirming that the absorption of isocyanate groups had disappeared, the reaction was completed. The obtained product is designated as B1.

Production Example 2 Both ends alcoholic hydroxyl group silicone (KF-6001 manufactured by Shin-Etsu Chemical Co., Ltd.), hydroxyl value 58 mg KOH /
g) 1500 parts, 4.0 parts of adipic acid, and 260 parts of hexamethylene diisocyanate were placed in a reaction vessel, heated and uniformly dissolved, and then reacted at a system temperature of 100 ° C. for 3 hours to obtain terminal isocyanate groups. A urethane prepolymer containing 7% (per solid) was obtained. Set the system temperature to 8
The temperature was adjusted to 0 ° C., 69 parts of methyl ethyl ketoxime was gradually added with stirring, and the mixture was reacted at the same temperature for 60 minutes to obtain a half-block urethane prepolymer containing 1.8% (per solid) of terminal isocyanate groups. Next, set the system temperature to 5
The temperature was adjusted to 0 ° C., 167 parts of γ-aminopropyltriethoxysilane was gradually added with stirring, and the reaction was continued at the same temperature for 30 minutes. After confirming that the absorption of isocyanate had disappeared, the reaction was completed. The obtained product is designated as B2.

Example 1 A mixture of 380 parts of octamethylcyclotetrasiloxane and 20 parts of B1 of Production Example 1 was added to a solution of dodecylbenzenesulfonic acid in 580 parts of water, which was previously mixed and dissolved, with stirring, and a Gaulin homogenizer was further added. 4 using
The treatment was performed twice at 00 kg / cm ² . 8
After heating and stirring at 0 ° C. for 3 hours, the temperature was lowered to 30 ° C. while stirring under cooling, followed by aging at the same temperature for 5 hours. Finally, the mixture was neutralized with an aqueous sodium hydroxide solution to obtain a silicone emulsion.

Example 2 330 parts of octamethylcyclotetrasiloxane and B22 of the preparation example were added to a solution prepared by mixing and dissolving 70 parts of lauryl trimethyl ammonium chloride in 575 parts of water in advance.
The mixture with 0 parts was added with stirring, 5 parts of a 50% aqueous potassium hydroxide solution was further added, and the mixture was treated twice with a Gaulin homogenizer at 400 kg / cm ² . The obtained emulsion was heated and stirred at 80 ° C. for 3 hours. The temperature was lowered to 30 ° C. while stirring under cooling, and after aging at the same temperature for 5 hours,
Neutralized with hydrochloric acid to obtain an emulsion.

Example 3 300 parts of octamethylcyclotetrasiloxane and 300 parts of lauryltrimethylammonium chloride were previously mixed and dissolved in 575 parts of water with 575 parts of water.
The mixture with 50 parts was added under stirring, and 5% of a 50% aqueous solution of potassium hydroxide was further added. The mixture was treated twice with a Gaulin homogenizer at 400 kg / cm ² . The obtained emulsion was heated and stirred at 80 ° C. for 3 hours. The temperature was lowered to 30 ° C. with stirring under cooling, aged at the same temperature for 5 hours, and neutralized with hydrochloric acid to obtain an emulsion.

Example 4 A solution prepared by mixing and dissolving 70 parts of lauryltrimethylammonium chloride in 575 parts of water was mixed with 280 parts of octamethylcyclotetrasiloxane and B2 of Production Example 2.
50 parts and γ-aminopropyltriethoxysilane 20
The mixture was added with stirring, and 5 parts of a 50% aqueous potassium hydroxide solution was further added. The mixture was treated twice with a Gaulin homogenizer at 400 kg / cm ² . The obtained emulsion was stirred at 80 ° C. for 3 hours. While cooling, stir the temperature
The temperature was lowered to 0 ° C., aged at the same temperature for 5 hours, and neutralized with hydrochloric acid to obtain an emulsion.

Example 5 To 70 parts of the emulsion obtained in Example 1, 30 parts of colloidal silica (Snowtex S, manufactured by Nissan Chemical Industries, Ltd.) was uniformly mixed.

Example 6 To 70 parts of the emulsion obtained in Example 2, 30 parts of colloidal silica (Snowtex AK manufactured by Nissan Chemical Industries, Ltd.) was uniformly mixed.

Comparative Example 1 The procedure of Example 1 was repeated, except that the mixture of 380 parts of octamethylcyclotetrasiloxane and 20 parts of B1 was replaced with 400 parts of octamethylcyclotetrasiloxane. An emulsion for comparison was obtained.

Comparative Example 2 The procedure of Example 2 was repeated, except that 350 parts of octamethylcyclotetrasiloxane was used instead of the mixture of 330 parts of octamethylcyclotetrasiloxane and 20 parts of B2. I got an emulsion.

Evaluation of Emulsions The emulsions of Examples and Comparative Examples were evaluated for film formability, film properties, and storage stability.

Each emulsion is coated on a glass plate to a dry film thickness of about 20 μm, dried at room temperature for 2 days, and then heat-treated at 150 ° C. for 20 minutes and at 120 ° C. for 20 minutes to form a peelable film. The film formability was evaluated depending on whether or not it was performed.

The obtained film was evaluated for flexibility and toughness by handling, and visually evaluated for hue.

Each emulsion was stored in a transparent glass bottle with a lid and stored at 50 ° C. and 25 ° C. for one month, and the stability was evaluated by the presence or absence of abnormalities such as phase separation, viscosity increase, and gelation. The results are shown in the table below.

[0036]

[Table 1] Table 1 Example 1 2 3 4 Film formability: 105 ° C × 20 minutes None None None None 120 ° C × 20 minutes Yes Yes Yes With film properties: flexibility ¹⁾ ◎ ◎ ◎ ◎ Hue White White White White Toughness Yes Yes Yes Yes Storage stability: 50 ℃ x 1 month No abnormality No abnormality No abnormality No abnormality 25 ℃ x 1 month Same as above Same as above ─────────────────── ──────────────── 1) Flexible ◎ ＞ 〇 ＞ △ ＞ × Hard

[0037]

Table 2 Example Comparative Example 5 6 1 2 Film formability: 105 ° C × 20 minutes Yes Yes No No 120 ° C × 20 minutes Yes Yes No No Film properties: flexibility ¹⁾ ◎ ◎ ── ── Hue White White ── ── Toughness Yes Yes ── ── Storage stability: 50 ℃ × 1 month No abnormality No abnormality No abnormality No abnormality 25 ℃ × 1 month Same as above Same as above ─────────── ──────────────────────── 1) Flexible ◎ ＞ 〇 ＞ △ ＞ × Hard

Claims (4)

[Claims] 1. A silicone oligomer selected from (A) a cyclic diorganopolysiloxane or a linear diorganopolysiloxane having a silanol group and / or an alkoxysilyl group, and (B) at least one blocked isocyanate A silicone emulsion obtained by emulsifying an organosilicon compound having a group and an alkoxysilyl group with water in the presence of a catalyst for promoting the reaction between the component (A) and the component (B). 2. The silicone emulsion according to claim 1, wherein (C) a di-, tri- or tetraalkoxysilane is further added during the emulsification of the components (A) and (B). 3. The silicone emulsion according to claim 1, wherein said silicone oligomer is a cyclic dialkylpolysiloxane oligomer. 4. The silicone emulsion according to claim 1, further comprising colloidal silica.