| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | July 30, 2002 |
| PATENT TITLE |
Thermoplastic crosslinked product and heat-sensitive elastic adhesive |
| PATENT ABSTRACT | This invention is related to a thermoplastic crosslinked product obtainable by the crosslinking reaction of a composition comprising (A) a polymer having a silicon-containing group and (B) a tetravalent tin compound, said silicon-containing group having a hydrolyzable group bound to a silicon atom and capable of crosslinking through formation of a siloxane bond |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | May 30, 2000 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A method for expressing adhesiveness of a heat-sensitive elastic adhesive which comprises heating a thermoplastic crosslinked product, wherein said thermoplastic crosslinked product is obtained by the crosslinking reaction of a composition comprising (A) a saturated hydrocarbon polymer which has a silicon-containing group having a hydrolyzable group bound to a silicon atom and capable of crosslinking through formation of a siloxane bond and (B) a tetravalent tin compound, and said heat-sensitive elastic adhesive comprises the thermoplastic crosslinked product. 2. The method for expressing adhesiveness of a heat-sensitive elastic adhesive according to claim 1, wherein the polymer (A) comprises a repeating unit derived from isobutylene, and the total amount of the repeating unit derived from isobutylene in the polymer (A) accounts for not less than 50 weight %. 3. The method for expressing adhesiveness of a heat-sensitive elastic adhesive according to claim 1, wherein the tetravalent tin compound (B) is slected from the group consisting of dialkyltin dialkoxides and dialkyltin diacetylacetonates. 4. The method for expressing adhesiveness of a heat-sensitive elastic adhesive according to claim 1, wherein the fractional weight of the polymer (A) is less than 30% of the weight of the crosslinked product. 5. The method for expressing adhesiveness of a heat-sensitive elastic adhesive according to claim 1, wherein said silicon-containing group is represented by the general formula (1): ##STR2## wherein R.sup.1 and R.sup.2 each independently represents an alkyl group of 1 to 20 carbon atoms, an aryl group of 6 to 20 carbon atoms, an aralkyl group of 7 to 20 carbon atoms, or a triorganosiloxy group of the formula (R').sub.3 SiO-- (R' each independently represents a substituted or unsubstituted hydrocarbon group of 1 to 20 carbon atoms); X represents a hydrolyzable group; a represents any of 0, 1, 2 and 3 and b represents any of 0, 1, and 2 but both a and b are not concurrently equal to 0; m represents an integer of 0 to 19. 6. The method for expressing adhesiveness of a heat-sensitive elastic adhesive according to claim 1, wherein the polymer (A) is an isobutylene polymer. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION The present invention relates to a thermoplastic crosslinked product or heat-sensitive elastic adhesive which can be used with advantage as a sealing or adhesive having excellent workability and recyclability. PRIOR ART The sealant and adhesive in current use include hot-melt type and reactive sealant type. The hot melt type is predominantly composed of a thermoplastic elastomer and, for enhanced flexibility, contains a plasticizer such as mineral oil or paraffin oil. The hot melt type is superior in initial bond strength and workability but, because it is composed predominantly of a plasticized resin, is poor in heat resistance and weathering resistance. Moreover, because of its comparatively high plasticizer content, this adhesive is poor in antibleeding properties. The reactive sealant type is satisfactory in heat resistance and weathering resistance but poor in initial bond strength. Moreover, since it takes time for the adhesive to provide a necessary bond strength, the workability is unsatisfactory in some instances. Recently developed to overcome the shortcomings of said two types of adhesives is a reactive hot-melt material having the properties of a hot melt type and a reactive sealant type in one. SUMMARY OF THE INVENTION However, the reactive hot-melt material has the drawback that as the cure by reaction progresses, its thermoplasticity is lost to sacrifice workability and the material cannot be recycled any longer. The present invention has for its object to provide a thermoplastic crosslinked product or heat-sensitive elastic adhesive having the workability and recyclability of a hot-melt sealant and the rubber-like elasticity of a reactive type sealant. As the catalyst which catalyzes the hydrolysis of a hydrolyzable silicon group or the condensation catalyst, tin compounds are well known, and for the purpose of curing polymers containing such silicon groups, tin compounds are generally employed. It is also known that the rubber-like properties such as stress relaxation and memory characteristics of the cured product differ according to whether the tin compound used is divalent or tetravalent. The cured product obtained by using a divalent tin compound is low in stress relaxation and high in memory characteristic, thus being close to the ideal elastomer, but the use of a tetravalent tin compound results in high stress relaxation and low memory characteristics. A relevant phenomenon observed in the crosslinked product obtained by using a tetravalent tin compound is the plastic deformation which occurs under prolonged loading. The inventors of the present invention found that this phenomenon unique to the crosslinked product obtained by curing a silicon group-containing polymer with a tetravalent tin compound is promoted by heating of the cured product and have developed the present invention. The present invention, therefore, is directed to a thermoplastic crosslinked product obtainable by the crosslinking reaction of a composition comprising (A) a polymer having a silicon-containing group and (B) a tetravalent tin compound, said silicon-containing group having a hydrolyzable group bound to a silicon atom and capable of crosslinking through formation of a siloxane bond. The thermoplastic crosslinked product of the present invention shows thermoplasticity at a temperature lower than the thermal decomposition temperature of the main chain of the polymer. In a further aspect, the present invention is directed to a heat-sensitive elastic adhesive comprising the thermoplastic crosslinked product of the present invention, that is to say a crosslinked product which is fluid under heating and shows rubber-like elasticity at room temperature (in the ordinary service temperature range). BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a temperature-viscosity correlogram constructed by heat-melting the crosslinked products according to Example 1 and Example 5. DETAILED DESCRIPTION OF THE INVENTION The present invention is now described in detail. The term "thermoplastic crosslinked product" is used herein to mean a crosslinked product which shows plasticity by heating and rubber-like elasticity at room temperature (in the ordinary service temperature range). More concretely, the term means a crosslinked product which shows thermoplasticity at a temperature lower than the thermal decomposition temperature of the main chain of the polymer. The term "heat-sensitive elastic adhesive" is used herein to mean an elastic adhesive which is increased in bond strength when hot-pressed and specifically means an elastic adhesive such that adhesiveness is expressed by heating a condensation-crosslinked product of a hydrolyzable silicon group-containing saturated hydrocarbon polymer. The present invention is embodied by using a saturated hydrocarbon polymer (hereinafter referred to as saturated hydrocarbon polymer (A)) having at least one reactive silicon group containing a hydroxyl or hydrolyzable group bound to a silicon atom and capable of crosslinking through formation of a siloxane bond. The reactive silicon group mentioned above in the present invention is a well-known functional group and, as representative species thereof, includes groups of the general formula (1): ##STR1## [wherein R.sup.1 and R.sup.2 each represents an alkyl group of 1 to 20 carbon atoms, an aryl group of 6 to 20 carbon atoms, an aralkyl group of 7 to 20 carbon atoms, or a triorganosiloxy group of the formula R.sup.3.sub.3 SiO-- (R.sup.3 represents a monovalent hydrocarbon group of 1 to 20 carbon atoms; the three R.sup.3 s may be the same or different); when R.sup.1 or R.sup.2 occurs in two or more repeats, they may be the same or different; X represents hydroxy or a hydrolyzable group and when X occurs in two or more repeats, they may be the same or different; a represents an integer of 0 to 3; b represents an integer of 0 to 2; provided, however, that a+mb.gtoreq.1; b need not be the same over m repeats of (SiR.sup.1.sub.2-b X.sub.b O); m represents an integer of 0 to 19]. The hydrolyzable group in the above general formula (1) is not particularly restricted but may be a known hydrolyzable group. Specifically, however, hydrogen, alkoxy, acyloxy, ketoximato, amino, amido, aminooxy, mercapto, alkenyloxy, etc. can be mentioned. Among these, alkoxy groups are particularly preferred in view of the hydrolizability under mild conditions and ease of handling. The hydrolyzable group or hydroxyl group, mentioned above, may be attached, in the number of 1 to 3, per silicon atom and the preferred range of (a+mb) is 1 to 5. When said hydrolyzable group or hydroxyl group occurs in the number of two or more in the reactive silicon group, they may be the same or different. While the number of silicon atoms forming said reactive silicon group may be either one or two or more, the number of silicon atoms bound by, for example, siloxane bonding is preferably not more than 20. Particularly preferred from the standpoint of availability is a reactive silicon group of the general formula (2): --SiR.sup.2.sub.3-a X.sub.a (2) (wherein R.sup.2, X and a are respectively as defined above). The reactive silicon group exists in the number of at least one, preferably 1.1 to 5, per mole of the saturated hydrocarbon polymer. If the number of reactive silicon groups per molecule is less than one, curability will be insufficient and satisfactory rubber-like elastic properties may hardly be obtained. The reactive silicon group may be present at the molecular chain terminal of a saturated hydrocarbon polymer or present internally, or even present both terminally and internally. Particularly when the reactive silicon group is present at the molecular chain terminal, the amount of effective crosslinked chain length of the saturated hydrocarbon polymer component in the final crosslinked product is comparatively large with the result that an elastomeric crosslinked product with high strength and high elongation is more easily obtained. Saturated hydrocarbon polymers having said reactive silicon group may be used singly or in a combination of two or more species. The saturated hydrocarbon polymer for use in the present invention can be prepared by: (1) the polymerization of an olefinic compound of 1 to 6 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene and the like, as the main monomer or (2) the homopolymerization of a diene compound, such as butadiene, isoprene and the like or copolymerization thereof with said olefinic compound and subsequent hydrogenation, to mention just a few examples. From the standpoint of ease of introduction of the functional group at the terminal, ease of molecular weight control, and the ease of increasing the number of functional groups which can be introduced, the preferred saturated hydrocarbon polymer is an isobutylene polymer, a hydrogenated polybutadiene polymer or a hydrogenated polyisoprene polymer. The isobutylene polymer mentioned just above may be such that all the monomer units thereof are isobutylene units or may contain a monomer component copolymerizable with isobutylene in a proportion of preferably not more than 50% (weight %; the same applies hereinafter), more preferably not more than 30%, still more preferably not more than 10%. As such monomer components, there can be mentioned olefins of 4.about.12 carbon atoms, vinyl ethers, aromatic vinyl compounds, vinylsilanes, and allylsilanes, among others. Specifically, said copolymer component includes 1-butene, 2-butene, 2-methyl-1-butene, 3-methyl-1-butene, pentene, 4-methyl-pentene, hexene, vinylcyclohexane, methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, styrene, .alpha.-methylstyrene, dimethylstyrene, p-t-butoxystyrene, p-hexenyloxystyrene, p-allyloxystyrene, p-hydroxystyrene, .beta.-pinene, indene, vinyldimethylmethoxysilane, vinyltrimethylsilane, divinyldimethoxysilane, divinyldimethylsilane, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, trivinylmethylsilane, tetravinylsilane, allyldimethylmethoxysilane, allyltrimethylsilane, diallyldimethoxysilane, diallyldimethylsilane, .gamma.-methacryloyloxypropyltrimethoxysilane, .gamma.-methacryloyloxypropylmethyldimethoxysilane and so on. The hydrogenated polybutadiene polymer and other saturated hydrocarbon polymers mentioned above, too, as it is the case with said isobutylene polymer, may contain other monomer units in addition to the main monomer units. Furthermore, the saturated hydrocarbon polymer for use as (A) component in the present invention may contain, within the range conducive to the object of the invention, such monomer units which would remain double bonds after polymerization, e.g. polyene compounds such as butadiene, isoprene, 1,13-tetradecadiene, 1,9-decadiene, 1,5-hexadiene, etc., in a small proportion, preferably within the range of up to 10%. The number average molecular weight of said saturated hydrocarbon polymer, preferably said isobutylene polymer, hydrogenated polyisoprene polymer or hydrogenated polybutadiene polymer, is preferably within the range of about 500 to 100000, and from the standpoint of ease of handling, a liquid polymer having a molecular weight of about 1000 to 40000 is particularly preferred. As to molecular weight distribution (Mw/Mn), a narrower distribution is preferred because the viscosity is lower as the distribution is narrower, with the molecular weight being held constant. The process for producing said reactive silicon group-containing saturated hydrocarbon polymer is now described in detail, taking an isobutylene polymer and a hydrogenated polybutadiene polymer as examples. Among species of said reactive silicon group-containing isobutylene polymer, a reactive silicon group-terminated isobutylene polymer can be produced by using an isobutylene polymer having terminal functional groups, preferably having functional groups at all of its terminals, which is obtainable by the polymerization technique called "inifer method" (a cation polymerization method using a certain compound which doubles as an initiator called "inifer" and as a chain transfer agent). Processes of this kind are described in Japanese Kokai Publication Sho-63-6003, Sho-63-6041, Sho-63-254149, Sho-64-22904 and Sho-64-38407. On the other hand, an isobutylene polymer having a reactive silicon group internally of its molecular chain can be produced by adding a reactive silicon group-containing vinylsilane or allylsilane to a monomer component composed predominantly of isobutylene and copolymerizing them. Furthermore, an isobutylene polymer having reactive silicon groups both terminally and internally can be produced as follows. Thus, in the polymerization for production of said isobutylene polymer having functional groups at terminals, a reactive silicon group-containing vinylsilane or allylsilane is copolymerized with the main component isobutylene monomer and, then, the reactive silicon group is introduced into terminals of the copolymer. The reactive silicon group-containing vinylsilane or allylsilane includes such specific compounds as vinyltrichlorosilane, vinylmethyldichlorosilane, vinyldimethylchlorosilane, vinyldimethylmethoxysilane, divinyldichlorosilane, divinyldimethoxysilane, allyltrichlorosilane, allylmethyldichlorosilane, allyldimethylchlorosilane, allyldimethyldimethoxysilane, diallyldichlorosilane, diallyldimethoxysilane, .gamma.-methacryloyloxypropyltrimethoxysilane and .gamma.-methacryloyloxypropylmethyldimethoxysilane, among others. The process for producing a hydrogenated polybutadiene polymer may for example be as follows. First, the hydroxyl group of a hydroxy-terminated hydrogenated polybutadiene polymer is converted to an oxymetal group such as --ONa and --OK. The polymer is then reacted with an organohalogen compound of the general formula (3): CH.sub.2.dbd.CH--R.sup.4 --Y (3) [wherein Y represents halogen such as chloro or iodo; R.sup.4 represents a divalent hydrocarbon group of the formula --R.sup.5 --, --R.sup.5 --Oc(.dbd.O)-- or --R.sup.5 --C(.dbd.O)-- (where R.sup.5 represents a divalent hydrocarbon group of 1 to 20 carbon atoms, preferably an alkylene group, a cycloalkylene group, an allylene group or an aralkylene group), more preferably a divalent group selected from the group consisting of --CH.sub.2 -- and --p--R.sup.6 --C.sub.6 H.sub.4 --CH.sub.2 -- (R.sup.6 represents a hydrocarbon group of 1 to 10 carbon atoms)], to thereby produce a hydrogenated polybutadiene polymer having olefinic terminal groups (hereinafter referred to sometimes as an olefinic group-terminated hydrogenated polybutadiene polymer), in the first place. The technology for converting the terminal hydroxyl group of a hydroxy-terminated hydrogenated polybutadiene polymer to an oxymetal group includes the method of reacting the polymer with an alkali metal, e.g. Na or K; a metal hydride, e.g. NaH; a metal alkoxide, e.g. NaOCH.sub.3 ; or a caustic alkali, e.g. NaOH or KOH. The above production process gives an olefinic group-terminated hydrogenated polybutadiene polymer whose molecular weight is substantially equal to the molecular weight of the starting hydroxy-terminated hydrogenated polybutadiene polymer but when it is desired to obtain a polymer of greater molecular weight, a polyvalent organohalogen compound containing two or more halogen atoms per molecule, such as methylene chloride, bis(chloromethyl)benzene, bis(chloromethyl)ether or the like, can be reacted prior to said reaction with an organohalogen compound of the general formula (3). The reaction of the resulting polymer with an increased molecular weight with the organohalogen compound of the general formula (3) can give an olefinic group-terminated hydrogenated polybutadiene polymer of increased molecular weight. The above organohalogen compound of the general formula (3) includes but is not limited to such species as allyl chloride, allyl bromide, vinyl(chloromethyl)benzene, allyl(chloromethyl)benzene, allyl(bromomethyl)benzene, allyl(chloromethyl)ether, allyl(chloromethoxy)benzene, 1-butenyl(chloromethyl)ether, 1-hexenyl(chloromethoxy)benzene and allyloxy(chloromethyl)benzene. Among these, allyl chloride is preferred because it is available at low cost and ready to react. Introduction of said reactive silicon group into an olefinic group-terminated hydrogenated polybutadiene polymer can be accomplished, just as it is the case with the production of said reactive silicon group-terminated isobutylene polymer, by way of the addition reaction of, for example, a hydrosilane compound resulting from binding of one hydrogen atom to a group of the general formula (1), preferably a compound of the general formula (4): HSiR.sup.2.sub.3-a X.sub.a (4) (wherein R.sup.2, X and a are respectively as defined hereinbefore), in the presence of a platinum catalyst. The hydrosilane compound resulting from binding of one hydrogen atom to a group of the general formula (1) includes but is not limited to halosilanes such as trichlorosilane, methyldichlorosilane, dimethylchlorosilane, phenyldichlorosilane, etc.; alkoxysilanes such as trimethoxysilane, triethoxysilane, methyldiethoxysilane, methyldimethoxysilane, phenyldimethoxysilane, etc.; acyloxysilanes such as methyldiacetoxysilane, phenyldiacetoxysilane, etc.; and ketoximatosilanes such as bis(dimethylketoximato)methylsilane, bis(cyclohexylketoximato)methylsilane and so on. Among these compounds, halosilanes and alkoxysilanes are particularly preferred. The proportion by weight of the. polymer (A) in the total crosslinked product is preferably less than 30%, more preferably less than25%, for insuring better thermoplasticity. The tetravalent tin compound for use as (B) component in the present invention includes dialkyltin dialkoxides such as dibutyltin dimethoxide, dibutyltin dipropoxide and so on. Among these, a dialkyltin dimethoxide such as dibutyltin dimethoxide is preferred. Moreover, chelate compounds such as dibutyltin-bis(acetylacetonate) and tin derivatives of hydroxyl-containing aromatic compounds, such as dibutyltin diphenoxide, can likewise be used with advantage. While the compound (B) of the invention acts as a silanol condensation catalyst, it can be used in combination with other silanol condensation catalysts insofar as the object of the invention can be accomplished. Such silanol condensation catalysts include titanic acid esters such as tetrabutyl titanate, tetrapropyl titanate, etc.; tin carboxylates such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diethylhexanoate, dibutyltin dioctanoate, dibutyltin dimethylmalate, dibutyltin diethylmalate, dibutyltin dibutylmalate, dibutyltin diisooctylmalate, dibutyltin ditridecylmalate, dibutyltin dibenzylmalate, dibutyltin maleate, dibutyltin diacetate, dibutyltin diphenoxide, tin octoate, dioctyltin distearate, dioctyltin dilaurate, dioctyltin diethylmalate, dioctyltin diisooctylmalate, dioctyltin diversatate, tin naphthenate, etc.; tin oxides such as dibutyltin oxide, dioctyltin oxide, etc.; reaction products of dibutyltin oxide with phthalic esters; dibutyltin bis(acetylacetonate); organoaluminum compounds such as aluminum tris(acetylacetonate), aluminum tris(ethylacetoacetonate), diisopropoxyaluminum ethylacetoacetate, etc.; chelate compounds such as zirconium tetraacetylacetonate, titanium tetraacetylacetonate, etc.; lead octoate; amine compounds such as butylamine, octylamine, laurylamine, dibutylamine, monoethanolamine, diethanolamine, triethanolamine, diethylenetriamine, triethylenetetramine, oleylamine, cyclohexylamine, benzylamine, diethylaminopropylamine, xylylenediamine, triethylenediamine, guanidine, diphenylguanidine, 2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine, 2-ethyl-4-methylimidazole, 1,8-diazabicyclo(5.4.0)undecene-7 (DBU), etc.; salts of such amine compounds with a carboxylic acid or the like; low molecular polyamides obtainable from an excess of a polyamine with polybasic acids; reaction products obtainable from an excess of a polyamine with epoxy compounds; amino-containing silane coupling agents such as .gamma.-aminopropyltrimethoxysilane, N-(.beta.-aminoethyl)aminopropylmethyldimethoxysilane, etc.; and other known silanol condensation catalysts inclusive of various acid catalysts and basic catalysts. These catalysts may be used-singly or in a combination of two or more species. The formulating amount of the silanol curing catalyst for (B) component, based on 100 parts (parts by weight; the same applies hereinafter) of the polymer (A), is preferably about 0.1 to 20 parts, more preferably 1 to 10 parts. If the formulating amount of the silanol curing catalyst is less than the above range, the curing speed may at times be reduced and, in some cases, the curing reaction will hardly proceed well. On the other hand, if the proportion of the silanol curing catalyst exceeds the above-mentioned range, local heating and foaming will take place during the curing process to interfere with the production of a satisfactory crosslinked product. In addition, the pot life of the composition is shortened to sacrifice workability. The composition of the present invention is preferably supplemented with water or a metal salt hydrate as a source of water necessary for the condensation curing of the polymer (A). As the metal salt hydrate, many hydrates available commercially can be liberally used and, as examples, alkaline earth metal salt hydrates and other metal salt hydrates can be mentioned. The preferred, among these, are alkali metal salt hydrates and alkaline earth metal hydrates, and more specifically, MgSO.sub.4.7H.sub.2 O, Na.sub.2 CO.sub.3.10H.sub.2 O, Na.sub.2 SO.sub.4.10H.sub.2 O, Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O, Na.sub.3 PO.sub.4.12H.sub.2 O, and Na.sub.2 B.sub.4 O.sub.7.10H.sub.2 O, among others, can be mentioned. The metal salt hydrate is preferably used within the range of 0.01 to 50 parts per 100 parts of the reactive silicon group-containing saturated hydrocarbon polymer. The more preferred range is 0.1 to 30 parts, the still more preferred range is 1 to 20 parts, and the most preferred range is 2 to 10 parts on the same basis. The metal salt hydrates mentioned above may be used singly or in a combination of two or more species. According to the specific characteristics required for intended uses, the composition of the present invention may contain optional components other than said components such as plasticizers, hindered phenol or hindered amine antioxidants, ultraviolet absorbers, light stabilizers, pigments, surfactants, and even tackifiers such as silane coupling agents, each in a suitable proportion. Among such components, the plasticizer is used to adjust the flow characteristic for improved workability, and although any ordinary plasticizer can be used, it is preferable to use a hydrocarbon compound well compatible with the (A) component polymer of the invention. Such plasticizers can be used singly or in combination. Moreover, even a plasticizer which, by itself, is poorly compatible with the polymer can also be used if it is used in combination with said hydrocarbon compound for improved compatibility. The thermoplastic crosslinked product according to the present invention can be obtained as an elastomer, which is rubber-like at room temperature, by mixing formulated amounts of (A), (B) and other said components by means of a mixer, a mixing roll or a kneader or dissolving them in a suitable quantity of a solvent and allowing the resulting formulation to stand at room temperature or under heating for several hours to about one week. The thermoplastic crosslinked product according to the present invention is useful as a heat-sensitive elastic adhesive which finds application in the electric/electronic field, as a water seal in civil engineering, or in such applications as buildings, ships, automobiles, rolling stock and furniture. Furthermore, since this adhesive adheres firmly to a broad range of adherends, such as glass, stone, ceramics, wood, synthetic resin and metal, under non-primer conditions, it can be used as various kinds of elastic adhesives. In addition, the heat-sensitive elastic adhesive of the invention adheres with good security to infrared-reflecting glass, iron, genuine aluminum, anodized aluminum, and polycarbonate resin, it can be used with advantage as a sealing material for laminated glass. The thermoplastic crosslinked product according to the present invention displays excellent workability upon heating and undergoes phase change between elastomeric consistency and fluidity on repeated cooling and heating so that it can be used with advantage as a sealing agent or an elastic adhesive. |
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