Ultrahigh molecular weight polyethylene particles and molded product made thereof

Patent metadata

Field	Value
Publication number	US-10316119-B2
Application number	US-201414904108-A
Country	US
Kind code	B2
Filing date	Jul 7, 2014
Priority date	Jul 10, 2013
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

To provide novel ultrahigh molecular weight polyethylene particles having a high melting point and exhibiting high crystallinity, thus capable of providing a molded product excellent in mechanical strength, thermal resistance and abrasion resistance.
Ultrahigh molecular weight polyethylene particles which satisfy that (1) the intrinsic viscosity (η) is at least 15 dL/g and at most 60 dL/g, (2) the bulk density is at least 130 kg/m 3 and at most 700 kg/m 3 , and (3) ΔTm (ΔTm=Tm 1 −Tm 2 ) i.e. the difference between a melting point (Tm 1 ) in 1st scan and a melting point (Tm 2 ) in 2nd scan, measured by a differential scanning calorimeter (DSC), is at least 11° C. and at most 30° C.

First claim

The invention claimed is:

1. Ultrahigh molecular weight polyethylene particles having:
an intrinsic viscosity (η) being at least 15 dL/g and at most 60 dL/g,
a bulk density being at least 130 kg/m 3 and at most 700 kg/m 3 ,
a difference between Tm 1 and Tm 2 (i.e. ΔTm=Tm 1 −Tm 2 ) being at least 11° C. and at most 30° C., where Tm 1 is a melting point (Tm 1 ) in 1st scan measured by a differential scanning calorimeter (DSC) at the time when the temperature is raised from 0° C. to 230° C. at a temperature raising rate of 10° C./min (1st scan), and Tm 2 is a melting point (Tm 2 ) in 2nd scan measured by DSC at the time when, then, after being left to stand for 5 minutes, lowering the temperature to −20° C. at a temperature lowering rate of 10° C./min and then being left to stand for 5 minutes, the temperature is again raised from −20° C. to 230° C. at a temperature raising rate of 10° C./min (2nd scan),
a content of titanium is less than 0.2 ppm, and
a molecular weight distribution (Mw/Mn) is larger than 3 and less than 6.

2. The ultrahigh molecular weight polyethylene particles according to claim 1 , wherein a content of titanium is less than 0.1 ppm.

3. The ultrahigh molecular weight polyethylene particles according to claim 1 , wherein a tensile strength at break (TS (MPa)) of a sheet molded as cooled at a mold temperature lower by from 10 to 30° C. than the melting point (Tm 2 ) in 2nd scan measured by the above, after heat compression with a pressing pressure of 20 MPa at a pressing temperature 190° C., satisfies the following relational expression (a):
TS≥≥ 1.35× Tm 2 −130  (a).

4. The ultrahigh molecular weight polyethylene particles according to claim 1 , wherein a breaking strength (MTS (MPa)) at the time when a heat compression molded sheet is melt-drawn at a temperature higher by 20° C. than the melting point (Tm 2 ) in 2nd scan measured by the above, is at least 2 MPa.

5. The ultrahigh molecular weight polyethylene particles according to claim 1 , wherein a breaking strength (MTS (MPa)) at the time of being melt-drawn, as measured in the above, and the intrinsic viscosity (η), satisfy the following relational expression (b):
MTS≥ 0.11×η  (b).

6. The ultrahigh molecular weight polyethylene particles according to claim 1 , wherein an average particle diameter is at least 1 μm and at most 1,000 μm.

7. The ultrahigh molecular weight polyethylene particles according to claim 1 , wherein a molecular weight distribution (Mw/Mn) is larger than 3 and less than 5.

8. The ultrahigh molecular weight polyethylene particles according to claim 1 , which are obtained by homopolymerization of ethylene or by copolymerization of ethylene and an α-olefin.

9. The ultrahigh molecular weight polyethylene particles according to claim 8 , wherein the α-olefin is propylene, 1-butene, 4-methyl-1-pentene, 1-hexene or 1-octene.

10. The ultrahigh molecular weight polyethylene particles according to claim 1 , which are obtained by a slurry polymerization method.

11. The ultrahigh molecular weight polyethylene particles according to claim 8 , which are obtained by polymerization in the presence of a metallocene catalyst.

12. The ultrahigh molecular weight polyethylene particles according to claim 11 , wherein the metallocene catalyst is obtained from a transition metal compound (A), an organically modified clay (B) which is modified by an aliphatic salt, and an organic aluminum compound (C).

13. A molded product obtained from the ultrahigh molecular weight polyethylene particles as defined in claim 1 .

Assignees

• Tosoh Corp

Inventors

• Inatomi Kei
• Hasegawa Saiki
• Abe Shigehiko

Classifications

• C08F4/65927

  two cyclopentadienyl rings being mutually bridged · CPC title

• C08F10/02 Primary

  Ethene · CPC title

• C08F4/65912

  in combination with an organoaluminium compound · CPC title

• C08F210/16

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title

• C08F110/02 Primary

  Ethene · CPC title