JPS629615B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for crosslinking halogenated butyl rubber,
In particular, it relates to a method that allows crosslinking at a relatively low temperature range of from outside temperature to 90°C. Conventionally, as a low-temperature crosslinking method for butyl rubber or halogenated butyl rubber, sulfur is used as a vulcanizing agent and a dithioate-based compound such as zinc dimethyldithiocarbamate, or a xanthate-based compound such as zinc isopropylxanthate is vulcanized. Methods of using it as a promoter are known. However, this method takes more than one day even at 90° C. to crosslink butyl rubber or halogenated butyl rubber, and is not suitable as a low-temperature crosslinking method. On the other hand, as another method,
A low-temperature crosslinking method that uses P-quinone dioxime and lead peroxide in combination is known, but this method shortens the usable life of the mixed rubber composition, carries the risk of lead damage, and is not suitable for health and safety reasons. There is also a problem. The inventors of the present invention attempted a series of studies in order to eliminate these drawbacks from the above-mentioned situation, and among them,
Among silane coupling agents that are generally used to increase the reinforcing properties of organic polymers with inorganic fillers, organic functional groups selected from amino groups, mercapto groups, and ureido groups and alkoxyl groups bonded to silane are used. , a silane coupling agent having a hydrolyzable group selected from acetoxy groups can be used satisfactorily as a crosslinking agent for halogenated butyl rubber,
The present inventors have discovered that the present invention is also useful. That is, the feature of the present invention is that the molecule contains an organic functional group selected from an amino group, a mercapto group, and a ureido group, and a hydrolyzable group selected from an alkoxyl group or an acetoxy group bonded to a silane. An object of the present invention is to use a silane coupling agent having a group of as a crosslinking agent for halogenated butyl rubber. The above silane coupling agent used in the present invention has the general formula

【formula】

【formula】

[Formula] Among these, X, X', and X'' are hydrolyzable groups bonded to a silicon atom, an alkoxy group or an acetoxy group, and Y is a group selected from various organic functional groups. selected groups, such as amino groups, mercapto groups,
or a ureido group, R is -R ₁ -,

[Formula] or an atomic group selected from -(R ₁ -O-R ₄ -) _o , where R ₁ , R ₃ , and R ₄ are an alkylene group or a phenylene group, and R ₂ is H or an alkyl group, respectively. show. Further, R' and R'' are alkyl groups, and n is 1 to 5. Specific examples of this silane coupling agent include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,
β-aminoethyltrimethoxysilane, β-aminoethyltriethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane,
N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, and the like. In addition, this silane coupling agent is usually used for halogenated butyl rubber with a low halogen content in an amount of 0.1 to 5.0, preferably 0.5 per mole of halogen in the halogenated butyl rubber.
For halogenated butyl rubber having a high degree of halogenation, the amount used is such as to give the desired crosslinking density depending on the application. That is, for example, if you want the crosslinked product to have appropriate rubber elasticity, for 100g of halogenated rubber,
Good results can be obtained by using the silane coupling agent in an amount of 0.005 to 0.05 mol, and if it is desired to obtain a crosslinked product with a higher crosslinking density, using 0.005 to 0.2 mol. Such silane coupling agents have an amino group, mercapto group, or ureido group as an organic functional group in the molecule, and a hydrolyzable group such as an alkoxy group or acetoxy group bonded to the silane. When blended with halogenated butyl rubber, this compound reacts with moisture and begins to crosslink at low temperatures below 90°C, but this crosslinking reaction occurs because the halogen atoms in the halogenated butyl rubber interact with the organic functional groups of the silane coupling agent. The hydrolyzable group of the silane coupling agent that reacts to form a chemical bond and is further bonded to halogenated butyl rubber is hydrolyzed to become a silanol group, and the same occurs in other silane coupling agents bonded to halogenated butyl rubber. It is presumed that crosslinking occurs through a dehydration condensation reaction with the silanol groups generated in . It is also conceivable that a condensation reaction occurs between the silanol group produced by hydrolysis and the alkoxy group or acetoxy group of another silane coupling agent by dealcoholization or acetic acid removal, resulting in crosslinking. Therefore, the important point of the present invention is to bond the silane coupling agent to the halogenated butyl rubber by reacting the organic functional group of the silane coupling agent with the halogen of the halogenated butyl rubber in a moisture-free state. At this time, if necessary, heat can be added to complete the reaction in a short time. or,
Good results can be obtained by heating at 100 to 140°C for about 20 minutes, but this is not the gist of the present invention. The reaction product of the coupling agent and halogenated butyl rubber obtained in this way does not undergo crosslinking in the absence of moisture and maintains its plasticity, so it can be stored in moisture-proof cans, sealant cartridges, or If stored in a bag made of plastic film with a low moisture permeability coefficient, such as polyethylene or polyvinylidene chloride, and immediately before use, open the can or bag and take it out into the atmosphere, it will absorb moisture from the atmosphere and rapidly crosslink. ,
It begins to exhibit properties as a crosslinked rubber. This coupling reaction is very far-fetched, and the diffusion of water into the rubber is the rate-determining factor, and the influence of ambient temperature is not very large. 3 even at 5℃
It loses its plasticity over a period of time. As mentioned above, the organic functional group of the silane coupling agent used in the present invention has the role of reacting with the halogen in the halogenated butyl rubber to bond the silane coupling agent to the halogenated rubber. Since it can be carried out in a fully equipped factory, the size of the reaction rate does not matter much. However, the storage stability of the hydrolyzable alkoxyl group and acetoxy group bonded to the other functional group, silane, and the subsequent dehydration condensation reaction or dealcoholization of the silanol groups following the hydrolysis reaction. , it is necessary that it does not have an adverse effect on the acetic acid removal reaction, etc. From this point of view, amino groups, mercapto groups, and ureido groups are effective as the organic functional groups of the silane coupling agent and suit the above purpose well. Next, the halogenated butyl rubber to which the present invention is applied includes brominated butyl rubber, chlorinated butyl rubber, etc., and the halogen content is in the range of 0.1 to 20 wt%, especially rubber with a halogen content of 0.5 to 4 wt% gives good results. give. In this case, if the halogen content exceeds 20wt%, the modulus of the polymer becomes too high and it loses its rubber elasticity, which is not suitable.If it is less than 0.1wt%, the number of crosslinking points becomes too small, so it is not suitable for the present invention. It is not effective and is not appropriate. Further, in the present invention, the crosslinking rate can be accelerated by using not only the silane coupling agent alone but also a catalyst for the coupling reaction of the silane coupling agent such as dibutyltin dilaurate. Other effective catalysts for promoting the condensation reaction include metal organic acid salts such as dioctyltin dilaurate, dibutyltin diacetate, and iron stearate, as well as ammonium carbonate and organic amines. Furthermore, in the crosslinking method of the present invention, a crosslinking agent such as a sulfur-based vulcanizing agent, a quinone oxime-based crosslinking agent, or a resin vulcanizing agent, which is used for crosslinking halogenated butyl rubber, is used in combination with the silane coupling agent. Also, reinforcing agents such as carbon black, fillers such as calcium carbonate, softeners, plasticizers, tackifiers, anti-softening agents, anti-aging agents, ultraviolet absorbers, antioxidants, ozone deterioration prevention Agents, lubricants, flame retardants, foaming agents, colorants, fungicides, etc. may be added. As mentioned above, the crosslinking method of the present invention using a silane coupling agent as a crosslinking agent for halogenated butyl rubber can be carried out in the atmosphere or in the presence of moisture such as water.
Because halogenated butyl rubber can be crosslinked at low temperatures ranging from outside temperatures to 90°C, it can be used in pressure-sensitive adhesive tapes, pressure-sensitive adhesive sheets, sealants, repair materials for rubber products, and when dissolved in solvents, adhesives, etc. In addition, it can be effectively used as a corrosion-resistant tape for exposed transport pipes or as a waterproof sheet for roofs. Examples will be further shown below, but it goes without saying that the present invention is not limited to these. Example 1 Comparison of each of the compositions according to the present invention, A to F, and each of G to I, by mixing butyl bromination, various coupling agents, and dibutyltin dilaurate at room temperature in the proportions shown in Table 1 using an open roll. A composition was obtained. A sheet with a thickness of 2 mm was made from the obtained composition, and 70
It was immersed in warm water at a temperature of 0.degree. C. to crosslink, and the network chain concentration was calculated using the Flory-Rehner equation. This network chain concentration is determined by taking a sample of 2 x 10 x 20 mm.
After swelling in cyclohexane at 25℃ for 72 hours, the interaction constant for the solvent was 0.433 from the measured swelling degree.
Calculated using The results are shown in Table 2.

【table】

【table】

[Table] Example 2 Various rubber compositions of J, K and comparatively L, M, N, and O by the method of the present invention were kneaded at room temperature using open rolls in the proportions shown in Table 3. Obtained. The obtained rubber composition was made into a sheet with a thickness of 2 mm and soaked in hot water at 50°C and 70°C or at 50°C and
It was left open at 80°C to examine changes in mechanical properties over time. Tensile strength (T _B ; which is a mechanical property)
Kg/cm ² ) and elongation (E:%) according to JISK-6301
A test piece prepared using a JIS No. 3 dumbbell was measured at a tensile speed of 500 mm/min. The results are shown in Table 4.

【table】

[Table] From the above results, it is clear that the silane coupling agent, which has an organic functional group selected from amino, mercapto, and ureido groups in its molecule, is fully effective as a low-temperature crosslinking agent for halogenated butyl rubber. It is confirmed that the method of the present invention is an excellent method for low-temperature crosslinking of halogenated butyl rubber.

Claims (1)

[Claims] 1. When crosslinking halogenated butyl rubber, the crosslinking agent is an organic functional group selected from an amino group, a mercapto group, or a ureido group, and a hydrolyzable hydrolyzable group selected from an alkoxyl group or an acetoxy group bonded to a silane. 1. A low-temperature crosslinking method for halogenated butyl rubber, the method comprising using a silane coupling agent having a group.