JPH066634B2 - Method for producing surface-modified fluorinated elastomer vulcanized molded article - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel method for producing a surface-modified fluorine-containing elastomer vulcanized molded article. More specifically,
TECHNICAL FIELD The present invention relates to a method for producing a fluorinated elastomer vulcanized molded article having a vulcanization density that gradually decreases from the surface toward the inside and showing stable non-adhesion and low friction over a long period of time.

2. Description of the Related Art Conventionally, vulcanized fluoroelastomer moldings have been widely used in fields such as automobiles, industrial machines, and chemical plants. When this fluorinated elastomer vulcanization molded product is used for a member that comes into contact with other objects such as an automobile intake / exhaust system, a fuel system control valve, other mechanical valves and O-rings, gaskets, cables and fixing rolls of copying machines, It is necessary that the surface be non-sticky.

The surface modification method of such rubber elastic body has hitherto been, for example, a method using fluorine gas or a secondary amine, or a surface treatment with metallic sodium in liquid ammonia so that the surface is non-adhesive and has low friction property. Is known (Japanese Patent Laid-Open No. 61-247744).

However, in the former method, the surface of the molded product is often hardened to impair its properties as a rubber, and in the latter method, liquid ammonia and metallic sodium, which are highly dangerous, are used. Above, -70-
Since it is necessary to work in an ultra low temperature atmosphere of 35 ° C., it is not practical in terms of equipment and handling.

On the other hand, as a physical surface treatment method, for example, a fluororesin coating method, a high energy etching method, a deposit method and the like are known.

However, among these methods, none of the etching methods and the deposition methods using high energy have been sufficiently satisfactory in terms of detackification of the surface and low friction. Further, in the fluororesin coating method, although detackification and low friction are achieved to some extent, the obtained treated surface has a drawback that peeling occurs if used for a long period of time, and the treatment cost increases. I cannot escape.

On the other hand, a method of modifying the surface of the molded product by impregnating the surface of the fluorinated elastomer vulcanized product with a vulcanization accelerator optionally used in the polyhydroxy compound and vulcanizing again Proposed (JP-A-63-291930)
Issue). This method does not damage the rubber elasticity,
It can be said that it is a preferable method because it can achieve detackification and low friction to some extent. However, recently, there has been an increasing demand for a fluoroelastomer molded article exhibiting excellent non-adhesiveness even under more extreme use conditions, and in order to meet such a requirement, in this method, the impregnation treatment is performed. Therefore, it is necessary to carry out the treatment under extreme conditions, but in this case, there is a new problem such as an increase in hardness and a decrease in tensile properties.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention improves the drawbacks of the conventional method,
Fluorine-containing elastomer that can be dipped for a shorter period of time to impart more excellent non-adhesiveness and low frictional properties, to make it smaller than the increase in hardness and the decrease in tensile properties, and to maintain them stably for a long period of time. The purpose of the invention is to provide a vulcanized molded product.

Means for Solving the Problems The present inventor has conducted intensive studies to develop a surface-modified fluoroelastomer vulcanized molded product having the above-mentioned preferable properties, and from the surface of the fluorinated elastomer vulcanized molded product, It was found that the object can be achieved by impregnating a polyhydroxy compound with a specific compound and then vulcanizing, and the present invention has been completed based on this finding.

That is, according to the present invention, from the surface of the fluorinated elastomer vulcanization molded product, from (A) polyhydroxy compound and (B) organoquaternary ammonium hydroxide, organophosphonium hydroxide and bis (organophosphine) iminium hydroxide, The present invention provides a method for producing a surface-modified fluorine-containing elastomer vulcanized molded product, which comprises vulcanizing after impregnating at least one selected from the above.

Hereinafter, the present invention will be described in detail.

The fluorinated elastomer vulcanized molded article used in the method of the present invention, the fluorinated elastomer is blended with a vulcanizing agent and a vulcanization accelerator, and if necessary, a vulcanization accelerating activator,
Carbon black, metal oxides, metal hydroxides, antioxidants, lubricants and the like are vulcanized and molded,
It may be a primary vulcanization molded body or a secondary vulcanization molded body. Further, the fluorine-containing elastomer is not particularly limited as long as it can be polyhydroxy vulcanized. Examples of such a fluorine-containing elastomer include vinylidene fluoride-propylene hexafluoride copolymer, vinylidene fluoride-propylene hexafluoride copolymer, vinylidene fluoride-propylene hexafluoride-tetrafluoroethylene ternary copolymer Examples thereof include polymers and bromine- or iodine-containing copolymers thereof. These fluorine-containing elastomers may be used alone or in combination of two or more.

Examples of the main vulcanization method of the fluorine-containing elastomer include a polyhydroxy vulcanization method, a diamine vulcanization method, a peroxide vulcanization method, and the like, and a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerating activity to be used. The vulcanizing agent, vulcanization aid, and the like differ depending on the vulcanization method. For example, in the polyhydroxy vulcanization method, polyhydroxy compounds such as bisphenol AF, bisphenol A, and hydroquinone are used as the vulcanizing agent. Further, as the vulcanization accelerator, organo quaternary ammonium halide, organophosphonium halide, bis [organophosphine] iminium halide and the like are used, and as a typical example thereof, 8-benzyl 1,8-diaza-bicyclo [5,4,0] -7-undecenium chloride (DBUB'C), benzyltriphenylphosphonium chloride (BTPPC), bis (benzyldiphenylsulfophine) iminium chloride (BDPIC) and the like can be mentioned. Further, as the vulcanization accelerating activator which is added as necessary, sulfones and sulfoxides are used, and representative ones thereof are dimethyl sulfone and 4,4 ′.
-Dichlorodiphenyl sulfone, dimethyl sulfoxide and the like.

Further, in the diamine vulcanization method, as the vulcanizing agent, for example, N, N′-dicinnarimiden-1,6-hexanediamine, triethylenetetramine, ethylenediaminecarbamate, etc. are used. On the other hand, examples of the vulcanizing agent in the peroxide vulcanization method include dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and benzoyl peroxide. It is used in combination with monomers such as allyl isocyanurate, polyfunctional methacrylate, and N, N'-m-phenylene dimaleimide.

The carbon black added as necessary is not particularly limited, but generally MT, SRF, FEE,
Carbon such as FT is used. Further, as the metal oxide, for example, magnesium oxide, calcium oxide,
Lead oxide or the like is used, and as the metal hydroxide, for example, calcium hydroxide, magnesium hydroxide or the like is used.

Further, the lubricant that is added as necessary is not particularly limited as long as it is easily microdispersed in the fluorine-containing elastomer compound and does not repel the treatment liquid during the surface treatment described later.

In the method of the present invention, (A) a polyhydroxy compound which is a vulcanizing agent and (B) an organoquaternary ammonium hydroxide or an organophosphonium hydroxide which is a vulcanization accelerator, from the surface of the fluorinated elastomer vulcanized molded article. And after impregnating with at least one selected from bis (organophosphine) iminium hydroxide,
Vulcanization treatment is performed. Examples of the polyhydroxy compound as the treatment agent component (A) include bisphenol AF, bisphenol A, and hydroquinone. These may be used alone or in combination of two or more.

Examples of the organoquaternary ammonium hydroxide as the component (B) treating agent include, for example, tetramethylammonium hydroxide, triethylbenzylammonium hydroxide, 8-benzyl-1,8-diaza-bicyclo [5,4,
0] -7-undecenium hydroxide (DBUBH) and the like, and as the organophosphonium hydroxide, for example, triphenylethylphosphonium hydroxide, benzyltriphenylphosphonium hydroxide (BTPPH)
Examples of bis (organophosphine) iminium hydroxide include bis (triphenylphosphine) iminium hydroxide and bis (benzylphenylphosphine) iminium hydroxide (BDP).
IH) and the like. These (B) treatment agent components are 1
One kind may be used, two or more kinds may be used in combination, and a salt may be substantially formed with the polyhydroxy compound (A) treating agent component, or a dissociated state may be used.

Next, one example of preferred embodiments of the present invention will be described. First, (A) a polyhydroxy compound of a treating agent component, (B) a treating agent component, and vulcanization acceleration such as dimethyl sulfone used as necessary. The fluoroelastomer vulcanized molded article is dipped in a treatment solution prepared by dissolving an activator in a suitable organic solvent, and these agents are impregnated from the surface thereof, and then taken out and dried.

Regarding the organic solvent used in the treatment liquid, (A) the polyhydroxy compound of the treatment agent component and (B) the treatment agent component are dissolved, and the fluorine-containing elastomer vulcanized molded product is swollen, and the treatment liquid is taken out at the time of taking out. There is no particular limitation as long as it does not repel. Preferred solvents include, for example, acetone, methyl ethyl ketone, ethanol, ethanol, etc. These may be used alone or in combination of two or more.

The (B) treating agent component is obtained by, for example, dissolving a halide type compound exemplified as the vulcanization accelerator in an organic solvent and passing the solution through a strongly basic ion exchange resin column, or by adding sodium to the solution. An organic solvent solution containing an alcoholate, potassium alcoholate, sodium hydroxide, potassium hydroxide or the like is added, and the precipitated sodium halide or potassium halide is removed by a means such as filtration to obtain an organic solvent solution. Therefore, the treatment liquid can be prepared by dissolving the polyhydroxy compound (A) as the treatment agent component therein. In preparing this surface treatment solution, it does not matter if some water is contained.

Regarding the concentrations of the polyhydroxy compound of the treating agent component (A) and the treating agent component (B) in the treatment liquid, in order to increase the vulcanization density of the surface layer portion to increase the non-adhesiveness and the low frictional property. , It is better to increase the concentration. Further, the temperature and time of the dipping are appropriately selected depending on the swelling property and the concentration of the solvent, but if the dipping time is too long, the vulcanization density becomes high to the inside and the rubber elasticity is impaired, which is not preferable.
Therefore, high concentration and short time impregnation treatment is desirable.

Specifically, the concentration of the polyhydroxy compound of the treatment agent component (A) in the treatment liquid is usually 1 to 50% by weight, and the concentration of the treatment agent component (B) is usually selected in the range of 0.1 to 20% by weight. The dipping temperature is preferably in the range of 0 to 180 ° C, and the dipping time is short when the fluorine content of the fluorine-containing elastomer is small, and the dipping treatment is short because the swelling speed is fast, but when the fluorine content is large. On the contrary, since the swelling speed is slow, it is desirable to soak for a long time, usually 1 minute to 24 minutes.
Selected in a time range. Further, it is also important that the treating agent is uniformly attached to the surface in the drying process after the dipping so as to bring about non-tackiness.

Next, in this way, the molded body that has been subjected to the dipping and drying treatment is vulcanized, but the vulcanization is not particularly limited, but it includes a fluorine-containing elastomer, a vulcanizing agent, a vulcanization accelerator, etc. Depending on the type, the temperature and time should be selected appropriately so that excess vulcanizing agent and vulcanization accelerator are volatilized and decomposed so as not to deteriorate compression set and heat aging characteristics at high temperature of 150 ° C or higher. Is good.

By such a method, a surface-modified fluorine-containing elastomer vulcanized molded article having a large vulcanization density in the surface layer portion of the vulcanized molded article and having a vulcanization density gradually decreasing toward the inside can be obtained. If the vulcanization density of the surface layer portion is too much higher than that of the inside, the surface layer portion becomes too hard and elongation is lost, and the performance as an elastomer may not be sufficiently exhibited. Further, it is preferable that the reduction state of the vulcanization density is continuous, and if it becomes discontinuous, peeling easily occurs during long-term use.

The hardness of the surface-modified fluorine-containing elastomer vulcanized molded product obtained by the method of the present invention is not particularly limited, but is preferably in the range of JIS A hardness of 50 to 95. If this hardness is too low, the non-adhesiveness will be insufficient, and if it is too high, the sealing properties will be poor and there will be no elongation and brittleness.

The surface-modified fluorinated elastomer vulcanization molded product satisfying these conditions has no peeling of the surface layer or cracks at the time of tensile, and also has excellent rubber elasticity and lower tensile strength, elongation and compression set. Nonetheless, extremely excellent non-adhesiveness and low friction are imparted.

EFFECTS OF THE INVENTION According to the method of the present invention, it is possible to easily give a molded article having excellent non-adhesiveness and low frictional property without impairing the physical properties originally possessed as a fluorine-containing elastomer, and the above-mentioned performance is In addition to required applications, for example, control valves, oil seals, diaphragms, gaskets, O-rings, blade cables, etc., it is also suitably used for rolls such as fixing rolls of copying machines that require toner offset prevention.

Examples Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The adhesive strength was measured according to the following method.

That is, a rubber sheet (35 × 35 × 2 mm) is attached on a smooth base with heat-resistant double-sided tape, and a flat surface made of half steel (JIS S-45C) equipped with a weight receiving portion and a suspender on it. Place the ring in contact with the rubber sheet (the size of the ring is 25 mm in outer diameter and 19 mm in inner diameter, and the surface in contact with the rubber sheet is ground with # 1000 abrasive paper). Then, the total weight of the rubber sheet is 609g on the weight receiving part of the ring.
Place the weight so that it becomes / cm ² . The whole is placed in an oven at 120 ° C. and left for 20 hours, then taken out and allowed to cool for about 4 hours. When the temperature has dropped to 23 ° C, remove the weight, attach the ring to the rubber sheet, and attach it to the tensile tester including the load cell using the above-mentioned lifting tool,
Measure the tensile adhesion at a pulling speed of min.

Examples 1 to 5 After kneading with a 6-inch roll in the mixing ratio shown in Table 1, primary vulcanization was performed using a hot press under the conditions shown in Table 2 to obtain a sheet of 90 × 160 × 2 mm. Created.

Next, a surface treatment solution containing each accelerator of BDPIH, BTPPH, and DBUBH having the composition shown in Table 2 and bisphenol AF as a vulcanizing agent was first added to each of high-concentration solutions of BDPIC, BTPPC, and DBUBC to obtain sodium methylate. Inject and mix methanol solution containing equimolar amount of sodium chloride, filter and wash the precipitated sodium chloride, and wash the remaining solution with bisphenol AF.
Dissolved in methanol / acetone having a predetermined concentration =
It was prepared as a 1/1 (volume ratio) solution.

The vulcanized sheet was dipped in the treatment solution under the conditions shown in Table 2, air-dried overnight, and further dried at 120 ° C. for 60 minutes.

Next, secondary vulcanization was performed in the oven under the conditions shown in Table 2 to determine the adhesive strength and other physical properties.

The results are shown in Table 2.

Comparative Examples 1 to 6 Vulcanized sheets were prepared in the same manner as in Examples 1 to 5 using the compounding compositions shown in Table 1.

A surface treatment liquid containing vulcanization accelerators of BDPIC, BTPPC and DBUBC and bisphenol AF which is a vulcanization agent was prepared by dissolving them in methanol / acetone = 1/1 (volume ratio) to a predetermined concentration. .

Next, as for Comparative Example 1, as it is, Comparative Examples 2 to 6
For the above, the surface treatment was performed under the conditions shown in Table 2 in the same manner as in Examples 1 to 5, and then secondary vulcanization was performed.

The results are shown in Table 2.

As is clear from the comparison between Examples 1 and 2 and Comparative Examples 1 to 3, the comparison between Example 3 and Comparative Example 4, the comparison between Example 4 and Comparative Example 5, and the comparison between Example 5 and Comparative Example 6, The use of hydroxide type vulcanization accelerator achieves the same level of detackification with a shorter dipping time than the conventional halide type, where chloride type is used, and physical properties (tensile strength and elongation) are reduced. It turns out that becomes smaller. Shortening the dipping time will reduce the swelling of the fluororubber product during dipping, and in the case of vulcanized contact products with metal, it will also lead to the maintenance of its adhesive strength.

Claims (1)

[Claims] 1. From the surface of a fluorinated elastomer vulcanization molded article, from (A) polyhydroxy compound and (B) organoquaternary ammonium hydroxide, organophosphonium hydroxide and bis (organophosphine) iminium hydroxide. A method for producing a surface-modified fluoroelastomer vulcanized molded article, which comprises vulcanizing after impregnating with at least one selected.