JP2000198864A - Surface-modified rubber product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-modified rubber product whose surface frictional coefficient is reduced to improve the lubricity, and to provide a method for producing the same. SOLUTION: This surface-modified rubber product is obtained by forming a powdery silica layer on the surface of the rubber film comprising a rubber latex containing silica. Therein, the powdery silica constituting the layer is bound to the silica contained in the rubber film through siloxane bonds formed by the hydrolysis of a compound having two or more alkoxysilyl bonds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber product having a rubber film made of rubber latex, such as a rubber glove.
More specifically, the present invention relates to a surface-modified rubber product having a reduced coefficient of friction on the surface of a rubber film and improved lubricity, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, rubber products produced from rubber latex such as natural rubber latex, for example, rubber gloves, are too sticky as they are and are difficult to remove. By reducing the coefficient of friction (ie, tackiness) of the surface by methods such as powdering of talc, mica powder, starch, etc., attaching a release agent to the surface, and treating the surface with a halogen such as chlorine. , Improving the surface smoothness.

[0003] However, the above-mentioned method has a problem that the obtained powder contaminates foods and operation sites, and depending on the type of powder used, may cause allergic symptoms such as rash on the human body. For this reason, the above-mentioned method that does not use powder (powder-free) is the mainstream, but in such a method, chlorine used is toxic and causes environmental pollution such as generation of dioxin. There is a problem that the above considerations are required and that the obtained rubber product is discolored or colored with time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a surface-modified rubber product in which the various problems described above do not occur and the surface of a rubber film has improved lubricity. , And a method of manufacturing the same.

[0005]

In order to solve the above-mentioned problems, the surface-modified rubber product of the present invention has a fine powdery silica layer formed on the surface of a rubber film made of rubber latex containing silica. A surface-modified rubber product, wherein the finely powdered silica constituting the layer is bonded to silica present in the rubber film by a siloxane bond formed by hydrolysis of a compound having two or more alkoxysilyl bonds. It is characterized by having.

Further, the method for producing a surface-modified rubber product of the present invention is characterized in that a fine powdered silica is layered on the surface of a rubber film composed of a rubber latex containing silica through a compound having two or more alkoxysilyl bonds. After adhering to the surface of the rubber film, the compound is hydrolyzed, and the fine powdery silica constituting the layer is bonded to silica present in the rubber film through siloxane bonds.

According to the present invention, by forming a layer of fine powdered silica on the surface of the rubber film, the coefficient of friction (adhesion) of the surface of the rubber film of the rubber product is reduced, and the surface of the rubber film is smoothed. Performance can be improved. In addition, the fine powdered silica that forms the fine powdered silica layer is strongly bonded to the silica in the rubber film by siloxane bonds, so that the rubber can be pulled by work or washed with water or a solvent. There is no possibility of peeling off from the surface of the film, and the lubricity of the rubber product surface can be kept high for a long time.

Further, the production method of the present invention is a powder-free method, so there is no concern about contamination of foods and the like and allergy such as rash. In addition, since chlorine, which causes environmental pollution, is not used, the safety is high, and the resulting surface-modified rubber product is unlikely to be discolored or colored over time.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. The type of rubber latex used in the present invention is not particularly limited. For example, natural rubber latex such as natural rubber latex (NR) and deproteinized natural rubber latex (DPNR), isoprene rubber latex (IR), acrylonitrile-butadiene Copolymer rubber latex (NBR)
And the like, and synthetic rubber latex of these and the like and rubber mixtures thereof.

The silica used in the present invention is not particularly limited, and examples thereof include a powdered silica compound, silica magnesia, silica sol, and colloidal silica. In particular, colloidal silica is preferably used. In the present invention, in order to improve the dispersibility in the rubber latex, the average particle size of the primary particles (area basis) is 10 nm to 1 nm.
It is preferable to use silica having a thickness of 0 μm, preferably about 10 nm to 50 nm.

The amount of silica is preferably in the range of 1 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the solid rubber component of the rubber latex. When the amount of silica falls below the above range, two alkoxysilyl bonds are formed.
Since the amount of silica that binds to the silanol bond in the compound having at least one compound is insufficient, the bonding strength between the rubber film and the layer of fine powder silica may be weakened. On the other hand, even if the amount of silica exceeds the above range, no further effect is observed.

In the rubber latex, in addition to the above silica,
Various conventionally known additives such as a vulcanizing agent, a vulcanization accelerator, a vulcanization acceleration auxiliary (activator), an antioxidant, a filler, and a dispersant may be blended. Examples of the vulcanizing agent include sulfur and organic sulfur-containing compounds. The compounding amount thereof is 0.5 to 3 based on 100 parts by weight of the solid rubber component of the rubber latex.
It is preferably about parts by weight.

Examples of the vulcanization accelerator include PX (zinc N-ethyl-N-phenyldithiocarbamate) and PZ
(Zinc dimethyldithiocarbamate), EZ (Zinc diethyldithiocarbamate), BZ (Zinc dibutyldithiocarbamate), MZ (Zinc salt of 2-mercaptobenzothiazole), TT (Tetramethylthiuram disulfide) and the like. These can be used alone or in combination of two or more. The compounding amount is 0.5 to 3 with respect to 100 parts by weight of the solid rubber component of the rubber latex.
It is preferably about parts by weight.

Examples of the vulcanization accelerator include zinc white. The compounding amount is preferably 0.5 to 3 parts by weight based on 100 parts by weight of the solid rubber component of the rubber latex. In general, non-staining phenols are preferably used as the antioxidant, but amines may be used. The compounding amount of the antioxidant is preferably about 0.5 to 3 parts by weight based on 100 parts by weight of the solid rubber component of the rubber latex.

As the filler, for example, kaolin clay,
Hard clay, calcium carbonate and the like can be mentioned. The compounding amount is preferably 20 parts by weight or less based on 100 parts by weight of the solid rubber component of the rubber latex. In addition, a dispersant may be blended to improve the dispersion of the above additives in the rubber latex. Examples of such a dispersant include various anionic surfactants. The compounding amount of the dispersant is 0.3% by weight of the component to be dispersed.
It is preferably about 1.0% by weight.

In order to produce a rubber film as a base of a rubber film of a rubber product, for example, a rubber film of a rubber glove, from a rubber latex containing silica, a conventional dipping method, a heat-sensitive method, and a coagulation method are used in the same manner as before. The film may be formed by various conventionally known latex immersion methods. In the present invention, before forming a rubber film by the above-mentioned latex immersion method, rubber latex is previously prepared at 30 to 50 ° C. for 12 to 9 hours.
Pre-vulcanization may be performed under the condition of 6 hours. At that time, the silica may be blended after pre-vulcanizing the rubber latex.

If the pre-vulcanization temperature is lower than the above range, the pre-vulcanization takes time and the productivity may be deteriorated. Conversely, if the pre-vulcanization temperature is higher than the above range, the rubber latex may be unstable or the rubber latex surface may be dried. On the other hand, if the pre-vulcanization time is outside the above range, the pre-vulcanization may not proceed sufficiently or the reaction may proceed too much, and the physical properties of the obtained rubber film may be reduced.

The rubber film referred to in the present invention is an unvulcanized (excluding pre-vulcanized) rubber film obtained by forming a film by a latex dipping method using a rubber latex containing silica. Further, the rubber film referred to in the present invention is obtained by vulcanizing the above rubber film. Of the above-mentioned latex dipping methods, the usual dipping method is to dipped a glove type, or a woven or non-woven fabric (a backing material) formed into a glove type into a rubber latex containing the silica, pulled up, and dried. This is a method of forming a rubber film by repeating the step of making one or more times. In addition, the heat-sensitive method, in addition to the above additives, in a rubber latex further compounded with a heat-sensitive coagulant,
This is a method in which a preheated mold is immersed, gelled rubber latex is adhered to the surface thereof, and then pulled up and dried. Further, the adhesion method is a method in which cations (such as calcium ions) are adhered to the surface of a mold, and rubber particles in a negatively charged latex are agglomerated on the surface of the mold, then pulled up and dried. .

The rubber film obtained by the latex immersion method may be vulcanized at 100 to 130 ° C. for 20 to 60 minutes to form a rubber film. Used in the present invention, the alkoxysilyl (Si-OR ¹⁾ coupling a compound having two or more (hereinafter, simply referred to as the compound (1))
Is hydrolyzed by water or moisture to be converted into a compound having two or more silanol (Si-OH) bonds. The silanol (Si-
The OH) bond is formed by silica present in the rubber film and fine silica powder constituting the surface layer of the rubber film (described later).
And the silica present in the rubber film and the finely powdered silica in the above layer are firmly bonded by siloxane (Si-O) bonds.

As the compound (1), for example, the following general formula (1 ′):

[0021]

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(Wherein, R ¹ and R ² are the same or different and each represents an alkyl group, and R ³ and R ^{4 each} represent an organic group). Examples of the alkyl group corresponding to R ¹ and R ² in the general formula (1 ′) include, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl,
Examples include straight or branched chain alkyl groups such as t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decini, undecyl, dodecyl and the like. Among them, a linear or branched alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl and the like is preferable.

In the general formula (1 ′), R ³ and R ⁴
As the monovalent organic group corresponding to, for example, an alkyl group,
Examples thereof include an alkoxy group, an aryl group, and an aralkyl group. Specifically, examples of the alkoxy group include methoxy, ethoxy, propoxy, isopropoxy, butoxy, t-butoxy, pentyloxy, hexyloxy,
And alkoxy groups such as heptyloxy and octyloxy. Among them, methoxy, ethoxy, propoxy,
An alkoxy group having 1 to 6 carbon atoms such as isopropoxy, butoxy, t-butoxy, pentyloxy, hexyloxy and the like is preferable.

Examples of the alkyl group include the same groups as the above-mentioned alkyl groups. Examples of the aralkyl group include benzyl, 1-phenylethyl, 2-phenylethyl, 3-phenylpropyl, 4-phenylbutyl, 5-
A linear or branched alkyl group having 1 to 6 carbon atoms in the alkyl portion such as phenylpentyl, 6-phenylhexyl, 1,1-dimethyl-2-phenylethyl, and 2-methyl-2-phenylpropyl group; Certain aralkyl groups are mentioned.

Examples of the aryl group include groups such as phenyl, naphthyl, anthryl and phenanthryl. In the surface-modified rubber product of the present invention, the silica in the rubber film and the layer of the fine powder silica formed on the surface of the rubber film are strongly bonded by a silanol bond.
It is preferable to use a tetraalkoxysilane compound in which both R ³ and R ⁴ in addition to R ¹ and R ² are alkoxy groups.

Specific examples of such a tetraalkoxysilane compound include, but are not limited to, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetraphenoxysilane and the like. According to the present invention, since a layer of fine powdered silica is formed on the surface of the rubber film of the rubber product, the frictional resistance of the surface of the rubber film is reduced, and the smoothness of the surface of the rubber film is improved. Can be. In addition, since the layer of finely powdered silica is firmly bonded to the rubber film of the rubber product, it is difficult to be pulled off during use of the rubber product or peeled off by water or an organic solvent, and has an excellent lubricating effect for a long time. It can be applied to the surface of a rubber film of a rubber product.

The compound (1) used in the present invention is in a liquid state before hydrolysis and has a viscosity of (A)
It is preferably a so-called solventless liquid compound (1), and more preferably a solventless liquid alkoxysilane compound (1 ′), which can be directly used without any solvent when forming the layer. And more preferably a solventless liquid tetraalkoxysilane compound.

The use of such a solventless liquid compound eliminates the need for a solvent when applied to the surface of a rubber film (or a rubber film) of a rubber product, and reduces the working environment during production. There is no need to worry about reduction or air pollution, and the manufacturing cost can be reduced. The term "liquid" as used in the present invention includes not only compounds which are liquid at room temperature but also those which are solid at room temperature, become liquid by heating, and can be applied to the surface of a rubber film without any solvent.

In order to attach a layer of fine powdered silica to the surface of a rubber film (or a rubber film when vulcanization is performed) via the compound (1), first, the rubber film is first treated with the compound ( Immersed in the solution of 1) or compound (1)
Is applied to the surface of the rubber film by a usual coating method such as spin coating or roll coating, and then dried. As described above, it is preferable to use a solventless liquid compound (1) that does not use a solvent at all in consideration of the production cost, environmental aspects, and the like.

The drying may be performed at room temperature to 60 ° C. for about 30 minutes to 2 hours. In the present invention, after drying,
Vulcanization may be performed at 130 ° C. for 20 to 60 minutes.
Application (or immersion) of compound (1) on the surface of the rubber film
The amount is usually in the range of 1 to 20 μm, preferably 1 to 5 μm, as expressed in the film thickness after drying. In the present invention, a basic catalyst such as butylamine or an acidic catalyst such as hydrochloric acid is added to the compound (1) solution as necessary in order to promote the hydrolysis and condensation reactions of the compound (1). You may.

Next, the finely powdered silica to be adhered in a layered form is a finely powdered form of the silica exemplified in the rubber latex. In particular, colloidal silica and silica sol are preferably used. More specifically, the fine powder form has an average primary particle size (based on area) of 10 μm or less, preferably 1 μm or less.
0 nm to 5 μm, more preferably 10 nm to 50 nm.

Then, a colloidal material obtained by dispersing the fine powdered silica in a solvent such as water (hereinafter referred to as silica dispersion) may be attached to the surface of the rubber film via the compound (1). . In the above-mentioned silica dispersion, the amount of the finely divided silica compounded in the solvent is usually in the range of 1 to 20 parts by weight, preferably 1 to 10 parts by weight based on 100 parts by weight of the solvent.

When the amount of the finely divided silica is less than the above range, the bond with the compound (1) by the silaxane bond is reduced, and as a result, the bonding force between the rubber film and the finely divided silica layer is weakened. There is a possibility that the layer of the finely powdered silica is peeled off from the surface of the rubber film of the obtained rubber product. Conversely, if the compounding amount of silica exceeds the above range, the thickness of the layer of finely powdered silica may be too large and cracks may occur. Further, the effect of further addition (that is, a decrease in the coefficient of friction)
Can not be obtained.

In order to adhere the finely powdered silica to the surface of the rubber film in a layered form, the rubber film (or rubber film) coated with the compound (1) is immersed in the silica dispersion or the silica dispersion is treated as described above. The coating is performed by applying the coating by the usual coating method described above and then drying. Drying may be performed at room temperature to 60 ° C. for about 30 minutes to 2 hours. And
When a rubber film is used, vulcanization may be performed under the above conditions.

The lubricity of the rubber film of the surface-modified rubber product thus obtained is usually expressed as a coefficient of static friction of 0.2 to 0.2.
0.8, preferably in the range of 0.4 to 0.6. The surface-modified rubber product is not limited to rubber gloves, but may be applied to conventionally known rubber products such as finger cots and rubber boots.

[0036]

The present invention will be described below in detail with reference to examples and comparative examples. Example 1 To a natural rubber latex having a rubber solid content of 60% by weight, sulfur,
Zinc white and zinc dibutyldithiocarbamate (BZ)
By weight natural rubber latex: sulfur: zinc white: BZ
= 100: 1: 1: 0.6 to prepare a latex composition, and then 5 parts by weight of colloidal silica (Snowtex N Nissan Chemical Co., Ltd.) was added to the latex composition. Pre-vulcanization was allowed to proceed at 40 ° C. for 24 hours.

On the other hand, a glove mold heated to 100.degree.
Calcium nitrate ethanol solution (coagulant)
Then, after dipping in a latex composition containing silica for 10 seconds and pulling up the mold at 300 mm / min, a tetraethoxysilane compound (silane coupling agent KBM803, Shin-Etsu Chemical (Manufactured by Kogyo Co., Ltd.) and vulcanized in an oven at 120 ° C. for 30 minutes. Use this glove mold as colloidal silica (see above)
After immersing for 30 seconds in a silica dispersion in which 20 parts by weight was dispersed in 100 parts by weight of water, the mold was pulled up at 300 mm / min and dried at room temperature for several minutes.

Next, the above rubber film was placed in an oven for 120 minutes.
The mixture was heated at a temperature of 30 ° C. for 30 minutes and removed from the mold to obtain a rubber glove having a rubber film thickness of about 0.4 mm. Example 2 A glove mold heated to 100 ° C. in the same manner as in Example 1 was immersed in the precured latex composition, and then vulcanized in an oven at 120 ° C. for 30 minutes. Then, the vulcanized glove mold is immersed in the solvent-free liquid compound (1 ′) (described above), dried at room temperature for several minutes, and then applied to the silica dispersion in the same manner as in Example 1. It was immersed, pulled up and dried at room temperature for several minutes. Finally, it is heated in an oven at 120 ° C. for 30 minutes, removed from the mold, and the thickness of the rubber film is about 0.4 mm.
I got rubber gloves.

Example 3 A rubber glove was obtained in the same manner as in Example 1 except that a trialkoxysilane compound (silane coupling agent Si69, manufactured by Degussa) was used as the solvent-free liquid compound (1 '). Was. Example 4 A rubber glove was obtained in the same manner as in Example 2, except that a trialkoxysilane compound (silane coupling agent Si69, manufactured by Degussa) was used as the solventless liquid compound (1 ′).

Comparative Example 1 Colloidal silica (described above) was not added to the latex composition prepared in Example 1, and pre-vulcanization was allowed to proceed at 40 ° C. for 24 hours. On the other hand, a glove mold heated to 100 ° C. was immersed in a 20% calcium nitrate ethanol solution (coagulant), and then this silica was added to a latex composition containing no silica.
Then, the mold was pulled up, dried, heated in an oven at 120 ° C. for 30 minutes, and removed from the mold to obtain a rubber glove having a rubber film thickness of about 0.4 mm.

Comparative Example 2 Colloidal silica (described above) was not added to the latex composition prepared in Example 1, and pre-vulcanization was allowed to proceed at 40 ° C. for 24 hours. On the other hand, a glove mold heated to 100 ° C. was immersed in a 20% calcium nitrate ethanol solution, and then this silica was immersed in a latex composition containing no additive under the same conditions as in Example 1, and the mold was pulled up and dried. After that, in the oven 1
Vulcanized at 20 ° C. for 30 minutes. Then, the glove mold was immersed in a silica dispersion under the same conditions as in Example 1, the mold was pulled up, dried, heated in an oven at 120 ° C. for 30 minutes, removed from the mold, and removed from the rubber film. About 0.4mm
I got rubber gloves.

Comparative Example 3 A rubber glove was obtained in the same manner as in Example 1 except that a latex composition containing 0.5 part by weight of colloidal silica (described above) was used. Comparative Example 4 A rubber glove was obtained in the same manner as in Example 2, except that a latex composition containing 0.5 part by weight of colloidal silica (described above) was used.

Comparative Example 5 A rubber glove was obtained in the same manner as in Example 1 except that a silica dispersion containing 1 part by weight of colloidal silica (described above) was used. Comparative Example 6 A rubber glove was obtained in the same manner as in Example 2, except that a silica dispersion containing 1 part by weight of colloidal silica (described above) was used.

The coefficient of static friction of the rubber gloves obtained in Examples 1 to 4 and Comparative Examples 1 to 6 was measured using a Haydon 10 machine (manufactured by Shinto Kagaku Co., Ltd.). The coefficient of static friction of the rubber glove after rubbing and washing (washing) in water was measured in the same manner as described above. Based on the above measurement results, the amount of silica in the rubber latex, the type and addition time of compound (1 ') (before and after vulcanization), and the silica concentration (% by weight) in the silica dispersion
The results are shown in Table 1 below.

[0045]

[Table 1]

It was found that the rubber gloves obtained in the examples maintained a low value of the static friction coefficient before and after washing without any change.

[0047]

According to the present invention, the tackiness of the surface of a rubber film of a rubber product is improved, and its effect is maintained unchanged for a long period of time without being changed by the use of a solvent or the like during work. it can. Further, the production method of the present invention is a powder-free method and does not use toxic chlorine or the like, so that there is no concern about contamination of foods and the like and allergies, and has high safety.

Furthermore, the surface-modified rubber product obtained by the present invention has an effect that discoloration or coloring with the lapse of time hardly occurs.

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Claims (3)

[Claims] 1. A surface-modified rubber product having a layer of fine powdered silica formed on the surface of a rubber film composed of a rubber latex containing silica, wherein the fine powdered silica constituting the layer is an alkoxysilyl. A surface-modified rubber product characterized by being bonded to silica present in a rubber film by a siloxane bond formed by hydrolysis of a compound having two or more bonds. 2. A method in which finely powdered silica is attached in a layered manner to a surface of a rubber film composed of a rubber latex containing silica through a compound having two or more alkoxysilyl bonds, and then the compound is hydrolyzed. A method for producing a surface-modified rubber product, comprising bonding finely powdered silica constituting a layer to silica present in a rubber film through a siloxane bond. 3. The method for producing a surface-modified rubber product according to claim 2, wherein the compound having two or more alkoxysilyl bonds is a solventless liquid alkoxysilane compound.