# US 6,297,315 B1 · Process for preparing polytrimethylene terephthalate

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 6,297,315 B1
- Document ID: US6297315B1
- Status: Granted
- Kind: B1
- Application number: 09/309,923
- Filed: 1999-05-11
- Granted: 2001-10-02
- Earliest claimed: 1999-05-11
- Assignees: Shell Oil Company
- Inventors: Ben Duh; Ye-Mon Chen; Ann Marie Corey
- Web page: https://patentgrep.com/patent/US6297315B1

## CPC

- B29B 9/16: Auxiliary treatment of granules
- C08G 63/88: Post-polymerisation treatment
- B29K 2067/00: Use of polyesters {or derivatives thereof}, as moulding material
- B29K 2995/0041: Crystalline
- B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS

## Abstract

The pelletized product of melt condensation polymerization of 1,3-propanediol and terephthalic acid (or alkyl ester thereof) is crystallized by immersion in water at a temperature within the range of 60 to about 100° C. Hot-water treatment increases the crystallinity of the polymer to at least about 35% and increases pellet density to about 1.33 g/cm3.

## Claims

### Claim 1

A process for reducing the self-adhesiveness of polytrimethylene terephthalate pellets comprising the steps of:
contacting melt-phase-polymerized polytrimethylene terephthalate pellets having an intrinsic viscosity of at least 0.4 dl/g with an aqueous liquid at a temperature within the range of 60 to 100° C. for a time sufficient to induce a degree of crystallinity of 35% to 45% in the polytrimethylene terephthalate pellets.

### Claim 2 (depends on 1)

The process of claim 1 in which the polytrimethylene terephthalate pellets have an intrinsic viscosity within the range of 0.5 to 1.0.

### Claim 3 (depends on 1)

The process of claim 1 in which the polytrimethylene terephthalate pellets are maintained in contact with the aqueous liquid for a time within the range of 3 seconds to 3 minutes.

### Claim 4 (depends on 1)

The process of claim 1 in which the aqueous liquid temperature is within the range of 65 to 85° C.

### Claim 5 (depends on 1)

The process of claim 1 which further comprises providing continuous pellet movement during contact with the aqueous liquid.

### Claim 6 (depends on 1)

The process of claim 1 in which the pellets are contacted with the aqueous liquid for a sufficient time to produce polytrimethylene terephthalate pellets having a glass transition temperature of at least 60° C.

### Claim 7 (depends on 1)

The process of claim 1 in which the polytrimethylene terephthalate pellets have a differential scanning calorimeter thermogram characterized by the absence of a cold crystallization peak.

### Claim 8 (depends on 1)

The process of claim 1 in which the crystallinity of the treated polytrimethylene terephthalate pellets is within the range of 36 to 45%.

### Claim 9 (depends on 1)

The process of claim 1 in which the treated polytrimethylene terephthalate pellets have an apparent crystallite size within the range of 10 to 13 nm.

### Claim 10 (depends on 1)

The process of claim 1 in which the polytrimethylene terephthalate pellets have a density of at least 1.33 g/cm3.