Polyamide pellets, method for producing polyamide pellets, and method for producing polyamide molded article

Patent metadata

Field	Value
Publication number	US-10786928-B2
Application number	US-201515329793-A
Country	US
Kind code	B2
Filing date	Jul 23, 2015
Priority date	Jul 30, 2014
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

The polyamide pellet of the present invention includes a polyamide including diamine units and dicarboxylic acid units, 50% by mole or more of the diamine units being derived from m-xylylenediamine, wherein a spherulite density of a skin portion of the pellet is 40,000 to 250,000/mm 2 .

First claim

The invention claimed is:

1. A polyamide pellet comprising a polyamide including diamine units and dicarboxylic acid units, 50% by mole or more of the diamine units being derived from m-xylylenediamine, wherein a spherulite density of a skin portion of the pellet being 40,000 to 250,000/mm 2 , wherein the polyamide pellet is obtained by a method comprising:
extruding and drawing out the polyamide in a molten state into a strand form,
cutting the polyamide in the molten state drawn in strand form while cooling with water to pelletize the polyamide,
further cooling the pelletized polyamide with water for 4 seconds or more, and
subjecting the further cooled and pelletized polyamide to solid-phase polymerization to obtain the polyamide pellet.

2. The polyamide pellet according to claim 1 , wherein a spherulite density of a core portion of the pellet is 10,000 to 40,000/mm 2 .

3. The polyamide pellet according to claim 1 , wherein 50% by mole or more of the dicarboxylic acid units in the polyamide are derived from an aliphatic dicarboxylic acid having 6 to 12 carbon atoms.

4. The polyamide pellet according to claim 3 , wherein the aliphatic dicarboxylic acid having 6 to 12 carbon atoms is adipic acid, sebacic acid, or a mixture thereof.

5. The polyamide pellet according to claim 1 , which satisfies a condition of the following formula (1):
−110 μeq/g≤([COOH]—[NH 2 ])≤110 μeq/g  (1)

wherein [COOH] represents a terminal carboxyl group concentration (μeq/g) of the polyamide and [NH 2 ] represents a terminal amino group concentration (μeq/g) of the polyamide.

6. The polyamide pellet according to claim 1 , which has a relative viscosity of 2.0 to 4.2.

7. The polyamide pellet according to claim 1 , wherein the spherulite density of the skin portion is 80,000 to 110,000/mm 2 .

8. The polyamide pellet according to claim 1 , which is obtained by solid-phase polymerization of a pelletized polyamide being in an amorphous state.

9. The polyamide pellet according to claim 8 , wherein the pelletized polyamide being in the amorphous state is one obtained by melt polycondensation.

10. The polyamide pellet according to claim 1 , which has a cross-sectional area of 5 to 13 mm 2 .

11. The polyamide pellet according to claim 10 , which is a polyamide pellet for high compression screw molding which is to be kneaded and molding-processed by a single screw extruder having a compression ratio of 2.0 to 4.0.

12. A method for producing a polyamide molded article, in which the polyamide pellets according to claim 10 are kneaded and then molding-processed to obtain the polyamide molded article, wherein
the polyamide pellets are kneaded in a cylinder having a single screw therein.

13. The method for producing a polyamide molded article according to claim 12 , wherein a compression ratio in the cylinder is 2.0 to 4.0.

14. The method for producing a polyamide molded article according to claim 12 , wherein
the screw comprises a feeding part, a compression part following the feeding part, and a metering part following the compression part, and
the feeding part, the compression part, and the metering part have lengths, with the total sum thereof converted to 1, of 0.40 to 0.55, 0.10 to 0.30, and 0.10 to 0.40, respectively.

15. A method for producing polyamide pellets, comprising the steps of:
extruding a polyamide in a molten state into a strand form, the polyamide being obtained by polycondensation of a diamine containing m-xylylenediamine in 50% by mole or more and a dicarboxylic acid,
cutting the polyamide extruded into the strand form while cooling with water to pelletize the polyamide, and then further cooling the pelletized polyamide with water for 4 seconds or more, and
subjecting the pelletized polyamide after water cooling further to solid-phase polymerization to obtain the polyamide pellets.

16. The method for producing polyamide pellets according to claim 15 , wherein the pelletized polyamide at the end of the water cooling has a temperature of 65° C. or lower.

17. The method for producing polyamide pellets according to claim 15 , wherein the polyamide extruded into the strand form is cut to be pelletized within 2 seconds after landing on the water.

Assignees

• Mitsubishi Gas Chemical Co

Inventors

• Tochihara Tatsuya
• Shinohara Katsumi
• Sato Kaname
• Kato Tomonori
• Mitadera Jun

Classifications

• B29B9/10 Primary

  by moulding the material, i.e. treating it in the molten state · CPC title

• B29B11/02

  by dividing preformed material, e.g. sheets, rods · CPC title

• B29B2009/125

  Micropellets, microgranules, microparticles · CPC title

• B29B9/065

  under-water, e.g. underwater pelletizers · CPC title

• C08G69/265

  from at least two different diamines or at least two different dicarboxylic acids · CPC title