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
2001-11-16
2003-07-29
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S199000, C525S206000, C525S209000, C525S214000, C525S232000, C525S238000, C525S240000, C525S241000, C422S131000, C422S134000, C422S135000, C422S136000, C422S137000, C422S138000
Reexamination Certificate
active
06599981
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an olefinic thermoplastic elastomer composition having excellent tensile properties and appearance when molded into a product.
An olefinic thermoplastic elastomer, being light and easy for recycling, is widely used for automobile parts, industrial machine parts, electronic/electric instrument parts, construction materials and the like as an energy-saving and resource-saving thermoplastic elastomer particularly as an alternate to a soft polyvinyl chloride and a vulcanized rubber.
A conventional olefinic thermoplastic elastomer, however, has the defect that it has poor tensile strength compared to a soft polyvinyl chloride and a vulcanized rubber, and improving this defect has been strongly desired.
Further, particularly in the case of forming into a sheet and extrusion forming into a profile, the appearance of the molded product is very important. Inferior appearance due to roughness, minute projections and so forth on the surface of the molded product damages the value of the product remarkably. JP-A-58-25340 proposes a technique for manufacturing an olefinic thermoplastic elastomer by a dynamic crosslinking method with a twin screw extruder. Although this method produces sheets or extrusion moldings with sharply improved appearance compared to ones manufactured with a single screw extruder, it is not necessarily satisfactory. The reason considered therefor is that kneading at high shearing velocity in a twin screw extruder generates much heat by shearing, whereby the crosslinking reaction proceeds rapidly to result in a tendency to lead to non-uniform crosslinking.
JP-A-9-95540 describes a manufacturing method with a screw composed of specific kneading discs. But, this method is apt to cause the above-mentioned poor appearance when the screw revolution is raised and the extrusion throughput per hour is increased in order to increase productivity.
The inventors earnestly studied to solve the above problem and have found that, in manufacturing an olefinic thermoplastic elastomer by dynamically crosslinking a polyolefin resin and a rubber component using a twin screw extruder, the use of a screw having specific kneading segment allows a reduction in shear-derived heat generation, and that an olefinic thermoplastic elastomer composition excellent in tensile strength and molding appearance can be obtained by performing the dynamic crosslinking at an appropriate rate. Further, the inventors have found, on the occasion of manufacturing an olefinic thermoplastic elastomer by dynamically crosslinking a polyolefin resin and a rubber component using a twin screw extruder, by performing the dynamic crosslinking under the specific conditions, emergence of fish eyes (gel-like minute mass) decreases remarkably, and thus the inventors have completed the present invention.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention intends to solve the problem as mentioned above in the prior art, and the object is to provide a method that can produce with good productivity an olefinic thermoplastic elastomer composition superior in tensile strength and molding appearance, as well as a method that can produce an olefinic thermoplastic elastomer composition wherein emergence of fish eyes (gel-like minute mass) is decreased markedly.
The present invention comprises the following inventions.
(i) A method for manufacturing an olefinic thermoplastic elastomer composition characterized in that, in manufacturing an olefinic thermoplastic elastomer composition comprising a polyolefin resin and a crosslinked rubber by dynamic crosslinking with a twin screw extruder, there is used a screw where at least one kneading segment (&agr;) is disposed, and the clearance between the vertex portion of the kneading segment (&agr;) (here, the vertex portion means a point or portion at the farthest distance from the center of gravity in the cross-section) and the cylinder inner wall of the extruder is {fraction (1/60)} or more to ⅙ or less of the screw diameter.
(ii) A manufacturing method according to the above (i), wherein a kneading segment (&bgr;) is disposed downstream the kneading segment (&agr;), which segment (&bgr;) has a ratio of the clearance between the vertex portion of the kneading segment (here, the vertex portion means a point or portion at the farthest distance from the center of gravity in the cross-section) and the cylinder inner wall of the extruder to the screw diameter which ratio is smaller than the ratio as set forth regarding the kneading segment (&agr;).
(iii) A manufacturing method according to the above (ii), wherein the kneading segment (&agr;) and the kneading segment (&bgr;) are adjacently disposed.
(iv) A manufacturing method according to any one of the above (i) to (iii), wherein the clearance between the vertex portion of the kneading segment (&agr;) (here, the vertex portion means a point or portion at the farthest distance from the center of gravity in the cross-section) and the cylinder inner wall of the extruder is {fraction (1/60)} or more to {fraction (1/10)} or less of the screw diameter.
(v) A manufacturing method according to the above (ii) or (iii), wherein the value is less than {fraction (1/60)}, which value is a ratio of the clearance between the vertex portion of the kneading segment (&bgr;) (here, the vertex portion means a point or portion at the farthest distance from the center of gravity in the cross-section) and the cylinder inner wall of the extruder to the screw diameter.
(vi) A manufacturing method according to any one of the above (i) to (v), wherein the kneading segment (&agr;) has the following features:
A1) the kneading segment having three vertex portions (a) in the cross-section (herein, the vertex portion means a point or portion at the farthest distance from the center of gravity in the cross-section),
A2) the vertex portion of the kneading segment being composed of a portion (a1) continuously twisted to the contrary direction relative to the screw rotary direction and a portion (a2) continuously twisted to the same direction relative to the screw rotary direction, respectively to the thickness direction, and
A3) the thickness of the kneading segment (the total of the thickness of a1 and that of a2) being 1.0 times or more of the screw diameter.
(vii) A method for manufacturing an olefinic thermoplastic elastomer composition characterized in that, in manufacturing an olefinic thermoplastic elastomer composition comprising a polyolefin resin and a crosslinked rubber by dynamic crosslinking with a twin screw extruder, a kneading segment (A) is disposed at least at one place of the screw, which segment (A) has the following features:
A1) the kneading segment having three vertex portions (a) in the cross-section (here, the vertex portion means a point or portion at the farthest distance from the center of gravity in the cross-section),
A2) the vertex portion of the kneading segment being composed of a portion (a1) continuously twisted to the contrary direction relative to the screw rotary direction and a portion (a2) continuously twisted to the same direction relative to the screw rotary direction, respectively to the thickness direction, and
A3) the thickness of the kneading segment (the total of the thickness of a1 and that of a2) being 1.0 times or more of the screw diameter.
(viii) A manufacturing method according to the above (vii), wherein there is used a screw disposed with the kneading segment (A) at least at one place and disposed with a kneading segment (B) at least at one place having the following features:
B1) the kneading segment having two vertex portions (b) in the cross-section (here, the vertex portion means a point or portion at the farthest distance from the center of gravity in the cross-section), and
B2) the vertex portion of the kneading segment having a structure twisted discontinuously to the thickness direction.
(ix) A manufacturing method according to the above (viii), wherein there is used a screw that has a structure disposed with the
Itoh Yuichi
Uchiyama Akira
Mitsui Chemicals Inc.
Nutter Nathan M.
LandOfFree
Method for manufacturing olefinic thermoplastic elastomer... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing olefinic thermoplastic elastomer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing olefinic thermoplastic elastomer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3089015