Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2002-04-01
2003-12-30
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C156S345420, C525S938000, C528S033000, C528S045000, C528S076000, C528S087000, C528S374000, C528S418000
Reexamination Certificate
active
06670445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to curable compounds having in its molecular skeleton a group that is easily dissociated by heating after curing, curable resin compositions containing such compounds and methods of easily disassembling cured materials.
2. Description of the Related Art
In recent years, recycling properties are required in various fields in consideration of friendliness to the environment and a reduction in costs. Also, in the field of automobiles, disassembling of members bonded to each other with urethane adhesives has been being studied. This requires heating at 200° C. or more for softening or liquefying the urethane adhesives to thermally decompose the main chain and involves a problem of generating poisonous gas and the like. On the other hand, if thermoplastic adhesives are used, generation of poisonous gases upon disassembling is prevented. However, in this case a heating device is required at the time of coating so that the cost is high and the workability is poor. On the other hand, thermoplastic resin products have a disadvantage that since their softening starts at relatively low temperatures, their physical properties at high temperatures are poor so that they cannot be used at sites that will be exposed to high temperatures.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a curable compound, a cured resin composition containing the curable compound, which is liquid and therefore has good workability before curing and which can be softened or liquefied at a temperature lower than the thermal decomposition temperature of the curable compound in a short time after curing as well as a method of easily disassembling a cured material therefrom.
The present inventors have made extensive studies on a curable resin composition that softens or liquefies at a temperature lower than its thermal decomposition temperature and a cured product can stably exist up to such a softening or liquefying temperature. As a result, they have found that by using a group that does not participate in crosslinking reaction and is dissociated above a temperature at which crosslinks are formed and below a temperature at which the bond formed by the crosslinking reaction or main chain is decomposed or dissociated, such as a hemiacetal ester group, and a group that participates in the crosslinking reaction, a resin composition having undergone curing can be liquefied or softened at a temperature lower than the temperature at which the bond formed by the crosslinking reaction or main chain is decomposed or dissociated in a short time. Thus, the present invention has been achieved.
Incidentally, it is known that the bond formed by hemiacetal esterification reaction between vinyl ether and a carboxylic acid is dissociated by heating and is stable at temperatures below the dissociation temperature (Chemical Abstract 43,6576d, 1949). Known technologies utilizing thermal dissociation of hemiacetal ester groups include a thermal latent curing agent which contains a carboxyl group-containing compound having a carboxyl group blocked and protected by hemiacetal ester reaction and which generates the carboxyl group by heating at the time of curing as disclosed in JP 2850897 B. However, no technology has been known yet which uses a compound having introduced in the skeleton thereof a hemiacetal ester group and being utilized for achieving recycling the resin from the cured product.
According to a first aspect of the present invention, there is provided a curable compound having at least one thermally dissociable group (a) and at least two groups (b) participating in crosslinking reaction. In a preferred embodiment, the curable compound has at least one thermally dissociable group (a) and at least two groups (b) participating in crosslinking reaction selected from the group consisting of an isocyanate group, a blocked isocyanate group, an alkoxysilyl group, an epoxy group, an acid anhydride group, an amino group, a latent amino group, a mercapto group and a carboxyl group.
Here, it is preferable that the thermally dissociable group (a) is a group represented by the following formula (1)
where R
1
, R
2
, and R
3
independently represent a hydrogen atom or a hydrocarbyl group having 1 to 18 carbon atoms and X represents an oxygen atom or a sulfur atom.
Also, it is preferable that the thermally dissociable group (a) is a hemiacetal ester group obtained by reaction between a carboxyl group and a vinyl ether group or a vinyl thioether group.
According to a second aspect of the present invention, there is provided a curable resin composition containing the curable compound.
According to a third aspect of the present invention, there is provided a method of easily disassembling a cured material, characterized by comprising heating a cured product obtained by curing the above-described composition to thermally dissociate the dissociable group (a) and to soften or liquefy the cured product.
Here, it is preferable that the group (b) participating in crosslinking reaction is selected from the group consisting of an isocyanate group, a blocked isocyanate group, an alkoxysilyl group, an epoxy group, an acid anhydride group, an amino group, a latent amino group, a mercapto group, a carboxyl group, an acrylate group and a hydroxyl group. It is more preferable that the crosslinking reactive group (b) is selected from the group consisting of an isocyanate group, a blocked isocyanate group, an epoxy group, an acid anhydride group, an amino group, a latent amino group and a carboxyl group.
It is preferable that the thermally dissociable group is a group represented by the following formula (1)
where R
1
, R
2
, and R
3
independently represent a hydrogen atom or a hydrocarbyl group having 1 to 18 carbon atoms and X represents an oxygen atom or a sulfur atom.
It is preferable that the thermally dissociable group (a) is a hemiacetal ester group obtained by reaction between a carboxyl group and a vinyl ether group or a vinyl thioether group.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be described in detail.
According to a first aspect of the present invention, there is provided a curable compound having at least one thermally dissociable group (a) and at least two groups (b) that participate in the crosslinking reaction selected from the group consisting of an isocyanate group, a blocked isocyanate group, an alkoxysilyl group, an epoxy group, an acid anhydride group, an amino group, a latent amino group, a mercapto group and a carboxyl group.
Here, the thermally dissociable group (a) means a group that does not participate in crosslinking reaction and is not dissociated at a temperature at which crosslinks are formed by the group (b) that participates in the crosslinking reaction but is dissociated at a temperature above a temperature at which crosslinks are formed and below a temperature at which the bond formed by the group (b) that participates in the crosslinking reaction or the main chain is decomposed or dissociated.
The thermally dissociable group (a) that the curable compound of the present invention has is not particularly limited as far as it is a group that is dissociated at a temperature above a temperature at which crosslinks are formed and below a temperature at which the bond formed by the crosslinking reaction or main chain is decomposed or dissociated as described above. Such groups preferably include those groups represented by the following formula (1).
where R
1
, R
2
, and R
3
independently represent a hydrogen atom or a hydrocarbyl group having 1 to 18 carbon atoms and X represents an oxygen atom or a sulfur atom.
The hydrocarbyl group having 1 to 18 carbon atoms represented by R
1
, R
2
, and R
3
may be either one of an aliphatic hydrocarbyl group, an alicyclic hydrocarbyl group or an aromatic hydrocarbyl group. Among these, an aliphatic hydrocarbyl group is preferred.
Examples of the aliphatic hydrocarbyl group include a methyl group, an ethyl group, a n-propyl g
Aylward D.
Rader & Fishman & Grauer, PLLC
The Yokohama Rubber Co. Ltd.
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