Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-04-04
2001-03-27
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S09200D, C525S168000, C525S186000, C525S194000, C525S375000, C528S407000
Reexamination Certificate
active
06207762
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a thermally reversible crosslinked matter and a hot melt resin comprising this crosslinked matter.
B. Background Art
A thermoplastic resin melts and thereby falls into a state of mold-processability when heated to high temperature, and then falls into a state of having strength durable to use when cooled. Therefore, the thermoplastic resin is widely and conveniently used in the world.
However, although the viscosity of the thermoplastic resin standing in a melted state due to heating, in general, fully satisfies the mold-processability, the strength or heat resistance of the thermoplastic resin is not high at temperature where the thermoplastic resin is used. Therefore, the use range of the thermoplastic resin is limited.
A block copolymer, represented by SIS (styrene-isoprene-styrene), forms a pseudocrosslinked structure due to concentration of high-Tg polymer blocks at normal temperature, and the viscosity of the block copolymer decreases at or above Tg so much that the pseudocrosslinked structure breaks and thereby falls into a state of mold-processability. Therefore, the block copolymer has the mold-processability at relatively high temperature and the strength or heat resistance at use temperature without conflict. However, because the pseudocrosslinked structure is dominated by Tg of the copolymer itself, there are problems in that the heat resistance is inherently deficient.
Many suggestions have been made that the above-mentioned problems of the thermoplastic resin should be solved by introducing into the thermoplastic resin a real, thermally reversible crosslinked structure, in other words, a crosslinked structure which breaks due to heating and then reverts due to cooling. However, any of these suggestions has problems.
JP-A-50-139135 and JP-A-51-019035 disclose thermoplastic resins in which acrylic polymers having carboxyl groups are crosslinked with metal ions. JP-A-56-014573 discloses a thermoplastic resin as produced by adding maleic anhydride to a low molecular polyisoprene and crosslinking with metal ions. In addition, JP-A-05-202345 discloses a thermoplastic resin comprising an acrylic polymer having carboxyl groups as neutralized with polyvalent metals. These thermoplastic resins containing metal-crosslinked structures are more excellent than the block copolymer, represented by SIS, with regard to the heat resistance, but have problems in that: the melt viscosity during heating is high (because the metal ion crosslinkage is so relatively strong that it is difficult to break even if heated), the thermal stability during heating is low (because, especially, in the case where an ester group is present in the polymer, the metal plays a catalytic part in forming a crosslinkage between organic high molecules, whereby a covalent bond is gradually formed between the organic high molecules), and the melting temperature gradually rises.
JP-A-58-125774 discloses a thermoplastic resin which comprises an acrylic polymer having carboxyl groups as neutralized with polyvalent metals and further comprises an o-methoxyaryl acid. This thermoplastic resin has effects in that its melt viscosity decreases during heating, when compared with the above-mentioned conventional metal ion-crosslinked matters, but has problems in that the melt viscosity of the crosslinked matter is too high when compared with a noncrosslinked one, and therefore, still in this case, the thermal stability during heating is poor because a covalent bond is gradually formed due to heating.
JP-A-52-065549 discloses a thermoplastic resin which comprises a mixture of a polymer containing acid groups with a polymer containing amino groups. JP-A-56-057865 discloses a thermoplastic resin as produced by copolymerizing (meth)acrylamide with an olefinic unsaturated mono- or dicarboxylic acid. JP-A-57-158275 discloses a thermoplastic resin which comprises a major proportion of an acrylic polymer having amino groups in the molecular inside and carboxyl groups at molecular terminals. These thermoplastic resins utilizing an ion crosslinkage as formed between the acid and the amino group also have problems in that: the formed ion crosslinkage is so strong that it is difficult to break even if heated, and the melt viscosity is therefore high; and a thermally irreversible amide bond is formed between the acid and the amino group, and therefore, still in this case, the thermal stability during heating is low.
SUMMARY OF THE INVENTION
A. Object of the Invention
An object of the present invention is to provide a thermally reversible crosslinked matter, which displays a sufficiently low melt viscosity during heating and is also excellent in the stability of the melt viscosity, and further to provide a hot melt resin comprising this crosslinked matter.
B. Disclosure of the Invention
The present inventors diligently studied to solve the above-mentioned problems, and as a result, found that if an amino groups-containing compound having a hindered structure (steric hindrance structure) is used as an amino groups-containing compound comprising a thermally reversible ion crosslinkage as formed between an acid group and an amino group, then a thermally reversible crosslinked matter can be obtained, wherein the thermally reversible crosslinked matter displays a sufficiently low melt viscosity during heating, has good thermal stability, and is excellent in the heat resistance or in the strength at use temperature.
The reason why such a thing occurs is inferred as follows: the hindered structure hinders the approach of the acid group and the amino group to each other due to steric hindrance and forms an ion crosslinkage with a moderate distance between both groups kept, so the crosslinkage is easy to break due to heating, and in addition, the formation of the irreversible amide bond can also be prevented.
Thus, a thermally reversible crosslinked matter, according to the present invention, comprises a compound (A)-based moiety and a compound (B)-based moiety, wherein both moieties are bonded to each other through a crosslinked structure. This crosslinked matter is characterized in that: the crosslinked structure includes a structure making steric hindrance, and breaks due to heating and then reverts due to cooling; and when the crosslinked structure breaks due to heating, the melt viscosity of the thermally reversible crosslinked matter decreases to not higher than twice the melt viscosity of compound (A) alone or the melt viscosity of compound (B) alone, whichever is higher, as heated at the same temperature that the thermally reversible crosslinked matter is heated at.
It is preferable that the crosslinked structure breaks due to heating and then reverts due to cooling, and that when the crosslinked structure breaks due to heating, the melt viscosity of the thermally reversible crosslinked matter decreases to not higher than the melt viscosity of compound (A) alone or the melt viscosity of compound (B) alone, whichever is higher, as heated at the same temperature that the thermally reversible crosslinked matter is heated at, because inherently excellent mold-processability is obtained.
There can be a modification in which: compound (A) is a compound containing two or more acid groups per molecule; compound (B) is a compound containing two or more hindered amino groups per molecule; and the molar ratio of the acid group to the hindered amino group (acid group/hindered amino group) is in the range of 0.1 to 10.
Although not especially limited, compound (A) can be at least one member selected from the group consisting of polyester compounds, polyepoxy compounds, (meth)acrylic polymers, styrenic polymers, styrenic block copolymers, diene polymers, olefinic polymers, and ethylene-vinyl acetate copolymers. It is preferable that the (meth)acrylic polymers among these thermoplastic polymers are block copolymers, because inherently excellent heat resistance is obtained.
A hot melt resin, according to the present invention, comprises a thermally reversible crosslinked
Kobayashi Nobuhiro
Yoshida Masatoshi
Nippon Shokubai Co. , Ltd.
Sanders Kriellion
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