JPS6333496B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION This invention relates to crosslinkable rubber/plastic compositions. Various methods have been known for crosslinking rubber or plastics, one of which is the so-called water crosslinking method in which crosslinking is performed in the presence of moisture. This method uses, for example, chlorinated polyethylene, polychloroprene, polyethylene, polypropylene,
For polymers such as polyvinyl chloride and ethylene-vinyl acetate copolymers, for example, the general formula RR'SiY ₂ (R is an olefinically unsaturated monovalent hydrocarbon group or a hydrocarbonoxy group, and each Y is a hydrolyzable R' is a group R or a group Y)
This was a method in which silanes represented by the following were mixed, grafted onto a silane graftomer in the presence of a grafting catalyst, and then brought into contact with moisture to carry out a silanol condensation reaction to effect crosslinking. According to this method, since polymers often contain impurities such as water and trace amounts of metal salts, the silane graftomer obtained by grafting as described above undergoes a silanol condensation reaction during storage. There were disadvantages such as the progress of crosslinking due to Among these polymers,
Polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymers have a relatively low gelation rate during storage, but chlorinated polyethylene, polyvinyl chloride, and polychloroprene, which contain large amounts of fillers or plasticizers, The gelation rate of such halogen-containing rubbers and plastics was quite high, making it almost impossible to store them for long periods of time. The present invention was made in view of the problems with conventional crosslinking methods. That is, the present invention relates to a crosslinkable rubber/plastic composition, which has a high moisture absorption rate at room temperature and absorbs crystallization water in the temperature range of 100°C to 180°C, in order to prevent the progress of gelation due to moisture during storage. Focusing on the anhydrous inorganic salts released,
The purpose is to add such an anhydrous inorganic salt to the composition. Due to this, at room temperature, for example, during storage,
The dry state is maintained by absorbing moisture from the composition, and the silane graftomer does not undergo a silanol condensation reaction and gel. Furthermore, during extrusion, crystallization water of the inorganic salt that has absorbed moisture is released by the heat, so crosslinking can be carried out without particularly supplying moisture from the outside. It is preferable to add the anhydrous inorganic salt to the rubber/plastic before carrying out the grafting treatment, but it may be added together with a silane grafting catalyst etc. during grafting. As mentioned above, the inorganic salt is anhydrous, has a high moisture absorption rate at room temperature, and has a temperature of 100°C to 180°C.
A material that releases crystal water at ℃ is desirable. If the crystallization water release temperature is less than 100°C, water will be released into the blend and the silanol condensation reaction will proceed, which is not desirable. In addition, if the temperature exceeds 180℃, there will be almost no moisture in the mixture after extrusion, and the silanol condensation reaction rate after extrusion will be low, making it difficult to make new contact with moisture. . Examples of such inorganic salts include sodium sulfate, sodium sulfite, magnesium sulfate, thallium sulfate, and strontium chloride. Preferred crosslinkable compositions of the present invention include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polychloroprene, or other rubber or plastic, based on 100 parts by weight of the above-mentioned 100°C to 180
₁ to 5 parts by weight of an anhydrous inorganic salt that releases water of crystallization in the temperature range of ' is preferably a mixture of 0.5 to 10 parts by weight of a silane represented by a hydrolyzable functional group and 0.01 to 5 parts by weight of a grafting catalyst.In the present invention, the proportion of the inorganic salt is 1 to 5 parts by weight. The reason for this is that if it is less than 1 part by weight, sufficient water absorption and removal action cannot be obtained, but if it is about 5 parts by weight, sufficient release of crystal water can be obtained, and if it exceeds this amount, the crosslinking will not be achieved. In addition, the organic silane to be reacted with the polymer is represented by the general formula _RSiR'3 , where R is a hydrocarbon group containing an olefinic unsaturated group, a mercabuto group, or an amino group; ' has a hydrolyzable functional group, and the R group is reactive with free radical sites generated in the polymer. Examples of such groups are vinyl, allyl, cyclohexenyl, cyclopentadi enyl, methacryloxypropyl, etc. In particular, in the case of a halogen-containing polymer, an organic silane containing a mercabuto group or an amino group is preferable.
_Alkoxy groups such as propyl, butyl, acyloxy groups such as formyloxy _, acetoxy or propionoxy, oxime groups such as -ON=C( _CH3 ) ₂ , -ON= _OCH3C2H5 and ON
=C( _C6H5 ) ₂ or substituted amino groups such _as alkylamino and arylamino groups such as -
Any hydrolyzable _organic group such as _NHCH3 , _{-NHC2H5 ,} and -NH( _C6H5 ). The silane preferably contains three hydrolyzable functional groups, more preferably r-
Examples include mercabutopropyltrimethoxysilane. The proportion of silane used depends in part on the reaction conditions and in part on the degree of modification desired in the polymer. And practically 0.5-10
Ranges up to parts by weight are preferred. Grafting catalysts for grafting polymers with the silanes described above are already known, and any such materials can be used in the present invention. This material is preferably an organic base such as triethylamine, hexamethylenediamine, diethylenetriamine, guanidine, DBU, DBN or triethylenediamine. The mixing ratio thereof is preferably 0.01 to 5 parts by weight. The present invention will be explained below using examples. Example In the case where chlorinated polyethylene was used as the polymer, its formulation is shown in Table 1.

【table】

[Table] Figure 1 shows the gelation rate of the silane graftomer when sodium sulfate was added as an anhydrous inorganic salt in the formulation shown in Table 1. The insolubilization rate in the figure was measured by immersing the sample in xylene at 120°C for 24 hours and using a conventional method. This result shows that the insolubilization rate varies greatly depending on the presence or absence of sodium sulfate and the amount added. That is, it can be seen that when sodium sulfate is added, water in the polymer is absorbed and removed, and the silanol condensation reaction of the silane graftomer does not proceed. This allows long-term storage. Example Table 2 shows the amount of addition of various inorganic salts and the corresponding water content in the silane graftomer when various inorganic salts were added under the same conditions as in the above example. The water content in the graftomer was measured by the Karl Fischer reagent method.

【table】

[Table] From Table 2, it can be seen that as the amount added increases, the amount of water decreases, indicating the ability of the inorganic salt to absorb and remove water. Example In the second example above, the silane graftomer was prepared by adding 3 parts by weight of each of sodium sulfate, sodium sulfite, and sodium tetraborate.
It was extruded at an extrusion temperature of 100°C to 180°C, the extruded product was left in a 0% RH atmosphere, and the crosslinking rate was measured. The results are shown in FIG. The insolubilization rate in the figure is
It was immersed in xylene at 120°C for 24 hours and measured according to a conventional method. The number of released crystal water and the decomposition temperature of the inorganic salt during crosslinking are as follows.

[Table] From Figure 2, it can be seen that for sodium sulfate and sodium sulfite, which have a decomposition temperature of 180°C or lower, heating during extrusion sufficiently releases crystal water and promotes crosslinking. It can be seen that when sodium tetraborate is heated at 200°C, crystal water is not sufficiently released and crosslinking is hardly promoted. Example In the case where polychloroprene was used as the polymer, its formulation is shown in Table 3.

[Table] Figure 3 shows the gelation rate of the silane graftomer when sodium sulfate was added as an anhydrous inorganic salt in the formulation shown in Table 3. The insolubilization rate in the figure was measured by a conventional method after immersion in tetrahydrofuran at 60°C for 24 hours. This result shows that even in the case of polychloroprene, the insolubilization rate varies greatly depending on the presence or absence of sodium sulfate and the amount added. As is clear from the above explanation, according to the present invention, the moisture absorption rate is high at room temperature and at 100°C.
At least before extrusion, anhydrous inorganic salts are added that release water of crystallization in the temperature range of ~180°C.
Alternatively, it is possible to provide a crosslinkable rubber/plastic composition that does not undergo gelation during storage.

[Brief explanation of the drawing]

Figure 1 is a graph showing the gelation rate of silane graftomer depending on the amount of inorganic salt added in chlorinated polyethylene, and Figure 2 is a graph showing the crosslinking rate depending on the type of inorganic salt in chlorinated polyethylene.
FIG. 3 is a graph showing the gelation rate of silane graftomer depending on the amount of inorganic salt added in polychloroprene.

Claims (1)

[Claims] 1. For 100 parts by weight of rubber or plastic,
1 to 5 parts by weight of an anhydrous inorganic salt that releases water of crystallization in the temperature range of 100 to 180°C, with the general formula RSiR' ₃ (wherein R is a hydrocarbon group containing an olefinic unsaturated group, a mercapto group, or an amino group). , R' is a hydrolyzable functional group) and 0.5 to 10 parts by weight of a grafting catalyst, respectively.