# US 8,696,957 B2 · Methods for microcellular injection molding

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

- Number: US 8,696,957 B2
- Document ID: US8696957B2
- Status: Granted
- Kind: B2
- Application number: 12/879,498
- Filed: 2010-09-10
- Published: 2012-03-15
- Granted: 2014-04-15
- Earliest claimed: 2010-09-10
- Assignees: Eveready Battery Company, Inc.
- Applicants: Eugene P. Dougherty, Jr.; Keith Edgett; Lih-Sheng Turng; Chris Lacey; Jungjoo Lee; Patrick J. Gorton; Xiaofei Sun
- Inventors: Eugene P. Dougherty, Jr.; Keith Edgett; Lih-Sheng Turng; Chris Lacey; Jungjoo Lee; Patrick J. Gorton; Xiaofei Sun
- Web page: https://patentgrep.com/patent/US8696957B2

## CPC

- B29C 44/348: {by regulating the temperature and/or the pressure, e.g. suppression of foaming until the pressure is rapidly decreased}
- A61F 13/2097: {method of manufacturing tampon applicators}
- C08J 9/122: {Hydrogen, oxygen, CO2, nitrogen or noble gases}
- B29L 2031/753: {Medical equipment; Accessories therefor (bloodbags, medical bags B29L2031/7148; artificial eyes B29L2011/0008)}
- C08J 2203/06: CO2, N2 or noble gases
- C08J 2203/08: Supercritical fluid
- Y02P 20/54: using solvents, e.g. supercritical solvents or ionic liquids
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- A61F: FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS (dental prosthetics A61C)
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

In a method of microcellular injection molding, a polymer and a supercritical fluid are processed. A condition of processing the polymer and/or the supercritical fluid is adjusted to control a weight of a plastic part and/or a surface characteristic of a plastic part produced. In another method of producing a plastic part using microcellular injection molding, a polymer is heated and melted and a supercritical fluid is added thereto. The resulting mix is a single-phase polymer-gas solution comprising the polymer and the supercritical fluid. The polymer and/or the supercritical fluid are adjusted to control the weight of the plastic part and/or a surface characteristic of the plastic part. Once adjusted, the melted polymer with the supercritical fluid is injected into a mold. Upon injecting the melted polymer and supercritical fluid, a pressure drop causes the supercritical fluid to nucleate in the melted polymer, thereby causing nucleation of bubbles.

## Claims

### Claim 1

A method of microcellular injection molding, comprising:
providing a polymer;
providing a supercritical fluid to the polymer;
processing the polymer and the supercritical fluid;
adjusting at least one condition of processing the polymer and the supercritical fluid to control at least one of a weight of a plastic part produced and a surface characteristic of the plastic part produced from the method of microcellular injection molding; and
injecting the processed polymer with the supercritical fluid therein into a mold;
wherein injecting the processed polymer with the supercritical fluid therein into the mold causes a pressure drop of about 0.5 bar to about 2.5 bar that causes the supercritical fluid to nucleate in the processed polymer.

### Claim 2 (depends on 1)

The method of claim 1, wherein adjusting at least one condition of processing the polymer and the supercritical fluid comprises determining a nucleation rate of bubbles of the supercritical fluid in the polymer and adjusting a flow of the supercritical fluid provided based on the determined nucleation rate.

### Claim 3 (depends on 1)

The method of claim 1, further comprising transforming the processed polymer and supercritical fluid to a metastable supersaturated solution.

### Claim 4 (depends on 3)

The method of claim 3, wherein transforming the processed polymer and supercritical fluid comprises injecting the processed polymer and supercritical fluid into a mold cavity.

### Claim 5 (depends on 1)

The method of claim 1, wherein providing the supercritical fluid comprises controlling a mass flow rate of the supercritical fluid.

### Claim 6 (depends on 5)

The method of claim 5, wherein the supercritical fluid is nitrogen and wherein the plastic part produced is a feminine hygiene product.

### Claim 7 (depends on 6)

The method of claim 6, wherein the concentration of the nitrogen is controlled to be about 0.03 wt. % to about 1 wt. %.

### Claim 8 (depends on 6)

The method of claim 6, wherein the concentration of the nitrogen is controlled to be about 0.08 wt. % to about 0.25 wt. %.

### Claim 9 (depends on 5)

The method of claim 5, wherein the supercritical fluid is carbon dioxide and wherein the plastic part produced is a feminine hygiene product.

### Claim 10 (depends on 9)

The method of claim 9, wherein the concentration of the carbon dioxide is controlled to be about 0.3 wt. % to about 3 wt. %.

### Claim 11 (depends on 9)

The method of claim 9, wherein the concentration of the carbon dioxide is controlled to be about 0.5 wt. % to about 2 wt. %.

### Claim 12 (depends on 1)

The method of claim 1, wherein the supercritical fluid is provided at a pressure of about 10 bar to about 300 bar.

### Claim 13 (depends on 1)

The method of claim 1, wherein the supercritical fluid is provided at a pressure of about 70 bar to about 150 bar.

### Claim 14

A method of producing a plastic part using microcellular injection molding, comprising:
providing a polymer;
heating the polymer to melt the polymer;
adding a supercritical fluid to the melted polymer to produce a single-phase polymer-gas solution;
adjusting at least one of the polymer and the supercritical fluid to control at least one of a weight of the plastic part and a surface characteristic of the plastic part; and
injecting the melted polymer with the supercritical fluid therein into a mold;
wherein injecting the melted polymer with the supercritical fluid therein into the mold causes a pressure drop of about 0.5 bar to about 2.5 bar that causes the supercritical fluid to nucleate in the melted polymer.

### Claim 15 (depends on 14)

The method of claim 14, wherein the supercritical fluid is nitrogen and wherein adjusting at least one of the polymer and the supercritical fluid comprises adjusting the concentration of the supercritical fluid added to the melted polymer to be about 0.03 wt. % to about 1 wt. %.

### Claim 16 (depends on 14)

The method of claim 14, wherein the supercritical fluid is nitrogen and wherein adjusting at least one of the polymer and the supercritical fluid comprises adjusting the concentration of the supercritical fluid added to the melted polymer to be about 0.08 wt. % to about 0.25 wt. %.

### Claim 17 (depends on 14)

The method of claim 14, wherein the supercritical fluid is carbon dioxide and wherein adjusting at least one of the polymer and the supercritical fluid comprises adjusting the concentration of the supercritical fluid added to the melted polymer to be about 0.3 wt. % to about 3 wt. %.

### Claim 18 (depends on 14)

The method of claim 14, wherein the supercritical fluid is carbon dioxide and wherein adjusting at least one of the polymer and the supercritical fluid comprises adjusting the concentration of the supercritical fluid added to the melted polymer to be about 0.5 wt. % to about 2 wt. %.

### Claim 19 (depends on 14)

The method of claim 14, wherein adjusting at least one of the polymer and the supercritical fluid comprises adjusting a pressure drop of the supercritical fluid to be about 1 bar to about 2 bar.

### Claim 20 (depends on 14)

The method of claim 14, wherein the polymer comprises low density polyethylene.

### Claim 21 (depends on 14)

The method of claim 14, wherein a pressure of the single-phase polymer-gas solution prior to injecting is about 10 bar to about 200 bar.

### Claim 22 (depends on 14)

The method of claim 14, wherein a pressure of the single-phase polymer-gas solution prior to injecting is about 30 bar to 100 bar.

### Claim 23 (depends on 14)

The method of claim 14, wherein the plastic part is a consumer product or personal care product.

### Claim 24 (depends on 23)

The method of claim 23, wherein the plastic part is a tampon applicator or an infant care product.

### Claim 25

A method of molding a tampon applicator, comprising:
providing a polymer comprising a low density polyethylene resin;
heating the polymer to melt the polymer;
adding nitrogen gas to the melted polymer to produce a single-phase polymer-gas solution;
adjusting at least one of the polymer and the nitrogen gas to control at least one of a weight of the tampon applicator produced and a surface characteristic of the tampon applicator produced;
injecting the melted polymer with the nitrogen therein into a mold; and
cooling the mold;
wherein injecting the melted polymer with nitrogen therein into the mold causes a pressure drop of about 0.5 bar to about 2.5 bar that causes cells of the nitrogen to nucleate in the melted polymer.

### Claim 26 (depends on 25)

The method of claim 25, wherein the mass flow rate of the nitrogen added to the melted polymer is about 0.045 kg/hr to about 0.055 kg/hr.

### Claim 27 (depends on 25)

The method of claim 25, wherein a pressure drop of the nitrogen is about 1 bar to about 2 bar.

### Claim 28 (depends on 25)

The method of claim 25, wherein a time to add the nitrogen gas to the polymer is about 0.65 seconds to about 0.75 seconds.