Patent Publication Number: US-2002002263-A1

Title: Curable composition

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
       [0001] The present invention relates to a curable composition which is good for a sealing material and a sealant for the use of buildings, automobiles, ships, and so on. More particularly, the present invention relates to a curable composition which has excellent durability, heat-resistance, and storage stability.  
       [0002] It is required for a sealing material and a sealant to have adhesive properties and elasticity to keep close adhesion with a member under movements and vibrations of the member. Various curable compositions have been developed to meet these requirements.  
       [0003] Conventional sealing materials tend to be deteriorated by movements or vibrations of members, changes of ambient temperature, or the like. Moreover, modulus of elasticity of a conventional sealing material becomes high in a condition of high temperature so that the sealing material could be destructed or ripped off a member with movements and vibrations of the member.  
       OBJECT AND SUMMARY OF THE INVENTION  
       [0004] It is an object of the present invention to provide a curable composition which is excellent in such properties as adhesive properties and strength. It is another object of the present invention to provide a curable composition having excellent long-term durability. Further, it is an object of the present invention to provide a curable composition which has few stringiness and improved workability.  
       [0005] A curable composition of the present invention comprises 100 parts by weight of a saturated hydrocarbon polymer having at least one silicon-containing group which has at least one hydroxyl or hydrolyzable group bonded to a silicon atom and is crosslinkable through formation of a siloxane bond, 1-100 parts by weight of a compound having at least one epoxy group at its end, and 1-100 parts by weight of mica. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0006] A curable composition of the present invention includes the aforementioned saturated hydrocarbon polymer, the compound having at least one epoxy group at its end, and the mica. The saturated hydrocarbon polymer has at least one silicon-containing group which has at least one hydroxyl or hydrolyzable group bonded to a silicon atom and is crosslinkable through the formation of a siloxane bond. By a method disclosed in Japanese Patent Publication H8-231758A, this saturated hydrocarbon polymer is prepared from an isobutylene polymer having functional groups at all their ends and including an alkoxysilyl group as shown in the following chemical formula.  
                 
 
     [0007] In the above chemical formula, each of R and R′ is lower alkyl containing 1-5 carbon atoms, R may be the same with R′, or may be different from R′, and “a” is an integer from 1 to 3. The molecular weight of this isobutylene polymer having functional groups at all its ends is 1,000-40,000. This polymer is wax-like or very sticky liquid at room temperature, and is prepared by a cationic polymerization method called Inifers method.  
     [0008] As examples of the saturated hydrocarbon polymer, which is suitably used in the present invention, having at least one silicon-containing group which has at least one hydroxyl or hydrolyzable group bonded to a silicon atom and is crosslinkable through the formation of a siloxane bond, polymers in “Epion” series manufactured by Kanegafuchi Chemical Industries Co., Ltd. are given and they have a chemical structure shown in the following chemical formula.  
                 
 
     [0009] wherein n is an integer from 5 to 400 and m is an integer from 5 to 400.  
     [0010] As for the compound having at least one epoxy group at its end, it is desirable that the main chain of the compound is an alkyl group and the compound has good compatibility with the aforementioned saturated hydrocarbon polymer. An example of that compound is expressed by the following chemical formula, which is transparent liquid at room temperature.  
                 
 
     [0011] wherein n is an integer from 1 to 1,000, preferably from 5 to 1000. When n is greater than 1,000, viscosity of the curable composition becomes too high and a number of epoxy groups becomes relatively low.  
     [0012] The amount of the compound having at least one epoxy group at its end is 1-100 parts by weight, preferably 5-40 parts by weight for 100 parts by weight of the aforementioned saturated hydrocarbon polymer. When the amount of the compound is less than 1 part by weight, heat resistance of the cured material becomes poor. When the amount of the compound is more than 100 parts by weight, the curing may have some problems.  
     [0013] The amount of mica is 1-100 parts by weight, preferably 1-30 parts by weight for 100 parts by weight of the aforementioned saturated hydrocarbon polymer. There is no restriction on the kind of mica. Both natural and synthetic mica can be used. The average particle size of mica is preferably not greater than 150 μm, most preferably in a range from 20 μm to 50 μm.  
     [0014] In addition, it is preferable to mix a plasticizer into the curable composition of the present invention.  
     [0015] The plasticizer is not limitative and any usual plasticizer can be used. However, it is recommended to use a plasticizer having good compatibility with ingredients of the curable composition.  
     [0016] The plasticizer used for the curable composition is preferably at least one compound selected from a group consisting of hydrocarbon compounds, paraffin chlorides, phthalates, non-aromatic dibasic acid esters, esters of polyalkylene glycols, phosphate esters, and the like.  
     [0017] Examples of the hydrocarbon compound are polybutene, hydrogenated polybutene, ethylene-α-olefin oligomer, α-methylstyrene oligomer, biphenyl, terphenyl, triaryl dimethane, alkylene triphenyl, liquid polybutadiene, hydrogenated liquid polybutadiene, alkyl diphenyl, partially hydrogenated terphenyl, paraffinic oils, naphthenic oils, atactic polypropylene, and the like.  
     [0018] Examples of phthalates are dibutyl phthalate, diheptyl phthalate, di(2-ethylhexyl) phthalate, butylbenzyl phthalate, butylphthalylbutyl glycolate, and the like.  
     [0019] Examples of non-aromatic dibasic acid esters are dioctyl adipate, dioctyl sebacate, and the like.  
     [0020] Examples of esters of polyalkylene glycols are diethylene glycol benzoate, triethylene glycol dibenzoate, and the like.  
     [0021] Examples of phosphate esters are tricresyl phosphate, tributyl phosphate, and the like.  
     [0022] Among these plasticizers, most preferable plasticizers are hydrocarbon compounds not having unsaturated groups, for example, hydrogenated polybutene, hydrogenated liquid polybutadiene, paraffinic oils, naphthenic oils, atactic polypropylene, etc., which have good compatibility with the ingredients of the curable composition and make improvements in weather resistance of the curable composition.  
     [0023] The amount of the plasticizer is preferably in a range from 10 to 200 parts by weight for 100 parts by weight of the aforementioned saturated hydrocarbon polymer.  
     [0024] The curable composition of the present invention may contain proper amounts of other additives which are usually added into a sealing material and a sealant, for example, fillers (heavy calcium carbonate, calcium carbonate treated with a fatty acid, humed silica, precipitated silica, carbon black, talc, titanium oxide, and the like), adhesion improvers (epoxy compounds, silane coupling agent, and the like), anti-aging agents (hindered phenols, mercaptanes, thiophosphates, thioaldehydes, and the like), moisture suppliers (water, hydrates of inorganic salts, and the like), ultraviolet light absorbers (hindered amines, benzotriazoles, and the like), antiozonants, light stabilizers, toners, and so on.  
     [0025] A curing agent including curing catalysts is mixed with the curable composition prior to the use of the curable composition. The curing agent preferably includes curing catalysts (tin catalysts such as tin dioctylate, dibutyltin dilaurate, dibutyltin bis-acetyl acetate, and the like), cocatalysts (tertiary amine compounds, and the like), plasticizers, fillers. The amount of the curing agent is preferably in a range from 5 to 20 parts by weight (0.3 to 5.0 parts by weight of the curing catalyst) for 100 parts by weight of the aforementioned saturated hydrocarbon polymer.  
     EXAMPLE 1  
     [0026] As the saturated hydrocarbon polymer having at least one silicon-containing group which has at least one hydroxyl or hydrolyzable group bonded to a silicon atom and is crosslinkable through the formation of a siloxane bond, “Epion EP505S” (manufactured by Kanegafuchi Chemical Industries Co., Ltd.) was used. A base material was prepared by mixing 100 parts by weight of the saturated hydrocarbon polymer with 67 parts by weight of colloidal calcium carbonate and 27 parts by weight of ground whiting as fillers, 37 parts by weight of paraffin hydrocarbon (PAO 5004) as the plasticizer, 2 parts by weight of an anti-aging agent, 3.3 parts by weight of titanium oxide, 3.3 parts by weight of water as the co-curing agent, and 5 parts by weight of mica.  
     [0027] To the base material, 6.7 parts by weight of the epoxy compound (Rikaresin EX-24 manufactured by Shin-Nihon Rika Co., Ltd.: this compound is expressed by the aforementioned chemical formula 3, wherein n is 12-14.) was added to prepare the curable composition.  
     [0028] The curable composition was cured by adding the curing agent consisting of 1.7 parts by weight of tin octylate and 0.5 parts by weight of lauryl amine. Properties of the cured material were measured according to JIS (The Japanese Industrial Standard) A5758 and the results are shown in Table 1. The viscosity and workability were measured right after adding the curing agent. Further, the loss of volume after heating, durability, and stringiness of the cured material were measured. Those results are also shown in Table 1.  
     EXAMPLE 2  
     Comparative Examples 1-5  
     [0029] Curable compositions were prepared in the same manner as Example 1 except that amounts of ingredients are shown in Table 1. These curable compositions were cured by curing agents shown in Table 1. Properties of cured materials were measured, the results of which are shown in Table 1.  
     [0030] In only the case of Comparative Example 3, the curable composition contained 10 parts by weight of low molecular weight hydrocarbon (IP1620 manufactured by Idemitsu Petrochemical Co., Ltd.).  
     [0031] Comparative Examples 4 and 5 were the same in their composition as Examples 1 and 2, respectively, except that mica was not added.  
                           TABLE 1                                      Examples   Comparative Examples                                             Components   1   2   1   2   3   4   5               Saturated hydrocarbon   100   100   100   100   100   100   100       polymer* 1         Filler   100   100   100   100   100   100   100       Plasticizer   37   37   43   43   —   37   37       Anti-aging agent   2   2   2   2   2   2   2       Water   3.3   3.3   3.3   3.3   3.3   3.3   3.3       Titanium oxide   4.7   4.7   4.7   4.7   4.7   4.7   4.7       Epoxy compound* 2     6.7   6.7   —   —   —   6.7   6.7       Low molecular weight   —   —   —   —   10   —   —       hydrocarbon* 3         Mica   5   5   5   5   5   —   —       Curing agent       Tin octylate   1.7   3.3   1.7   3.3   3.3   1.7   3.3       Lauryl amine   0.5   0.5   0.5   0.5   0.5   0.5   0.5       Viscosity(23° C.)   210   200   320   300   170   210   200       Strain 100% [P]       Workability   Good   Good   Poor   Poor   Fair   Good   Good                               to Fair   to Fair       Ordinary state   11   11   11   12   11   11   11       50% modulus [N/cm 2 ]       Heat resistance   14   15   17.5   19   20   14   15       (90° C.,       2 weeks)       50% modulus [N/cm 2 ]       Loss of volume after   10% or   10% or   10% or   10% or   10% or   10% or   10% or       heat resistance test   less   less   less   less   more   less   less       Durability 10030   Good   Good   Fair to   Fair to   Fair   Good   Good                   Poor   Poor       Stringiness   Good   Good   Good   Good   Good   Fair to   Fair to                               poor   poor                                          
 
     [0032] From the comparisons of Examples 1 and 2 with Comparative Examples 4 and 5, respectively, it has been found that the addition of mica decreases stringiness resulting in improvements of workability.  
     [0033] It has been found that low molecular weight hydrocarbon added in Comparative Example 3 is effective to decrease viscosity of the curable composition. However, once the cured material is exposed to surroundings of high temperature, the hydrocarbon evaporates, which leads to decreasing of modulus of elasticity and greater loss of volume. It has also been found that Rikaresin EX24 is very effective to decrease viscosity of the curable composition and that, after heating, the cured material containing Rikaresin EX24 has a small loss of volume, a small increase of modulus of elasticity and improved durability.  
     [0034] As resulted from Examples and Comparative Examples, the present invention provides a curable composition comprising liquid saturated hydrocarbon polymer having a reactive silicon-containing group, wherein the curable composition provides a cured material having only a small increase of modulus of elasticity at high temperature and excellent durability.