# US 11,110,635 B2 · Method of injection molding using ribs and apparatus therefor

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- Number: US 11,110,635 B2
- Document ID: US11110635B2
- Status: Granted
- Kind: B2
- Application number: 15/762,384
- Filed: 2016-09-23
- Published: 2018-09-27
- Granted: 2021-09-07
- Earliest claimed: 2015-09-25
- Assignees: Sabic Global Technologies B.V.
- Applicants: SABIC Global Technologies B.V.
- Inventors: Peter Neerincx; Ruud Heerkens
- Web page: https://patentgrep.com/patent/US11110635B2

## CPC

- B29C 45/1679: {applying surface layers onto injection-moulded substrates inside the mould cavity, e.g. in-mould coating [IMC] (applying suface layers after ejection B29C45/0053)}
- B29C 44/06: Making multilayered articles {(B29C44/0407 - B29C44/0492 take precedence)}
- B29C 44/086: {and feeding more material into the enlarged cavity}
- B29C 45/16: Making multilayered or multicoloured articles {(B29C45/0062 takes precedence; feeding colouring materials into the injection unit B29C45/1816)}
- B29C 45/1704: {the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles (B29C45/1732 and B29C45/1734 take precedence; injection blow-moulding B29C49/06)}
- B29C 44/355: {Characteristics of the foam, e.g. having particular surface properties or structure}
- B29C 2045/1682: {preventing defects}
- B29K 2023/06: {PE, i.e. polyethylene}
- B29K 2027/06: PVC, i.e. polyvinylchloride
- B29K 2027/18: PTFE, i.e. polytetrafluoroethylene {, e.g. ePTFE, i.e. expanded polytetrafluoroethylene}
- B29K 2033/04: Polymers of esters
- B29K 2055/02: ABS polymers, i.e. acrylonitrile-butadiene-styrene polymers
- B29K 2069/00: Use of PC, i.e. polycarbonates {or derivatives thereof}, as moulding material
- B29K 2071/00: Use of polyethers {, e.g. PEEK, i.e. polyether-etherketone or PEK, i.e. polyetherketone or derivatives thereof}, as moulding material
- B29K 2101/12: Thermoplastic materials
- B29K 2105/0005: {containing compounding ingredients (releasing, lubricating or separating agents B29C33/56, fibers B29K2105/08, B29K2105/12; fillers B29K2105/16, recycled material B29K2105/26)}
- B29K 2105/04: cellular or porous
- B29K 2995/0097: Thickness
- B29L 2031/3041: {Trim panels}
- 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)
- 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
- B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES

## Abstract

A method of injection molding parts, including: injecting a first thermoplastic polymer into a first cavity; forming a ribbed structure comprising ribs in the first cavity, wherein each rib in the ribbed structure includes a microstructure on an outer portion of a rib; and reducing the surface imperfections in the part by overmolding a layer formed in the second cavity onto a portion of a rib by injecting a second thermoplastic polymer into the second cavity, wherein the overmolding occurs at an interface between the layer and the ribbed structure; or injecting a first thermoplastic polymer into a first cavity; forming a layer in the first cavity; and overmolding a ribbed structure comprising ribs formed in the second cavity onto a portion of the layer formed in the first cavity. In further variations gas is injected into a microchannel formed at the interface or a foaming agent is applied in the first thermoplastic polymer.

## Claims

### Claim 1

A method of reducing surface imperfections in an injection molded part, comprising:
injecting a first thermoplastic polymer into a first cavity;
forming a ribbed structure comprising ribs in the first cavity, wherein each rib in the ribbed structure includes a microstructure on an outer portion of a rib; and
reducing the surface imperfections in the part by overmolding a layer formed in a second cavity onto a portion of a rib by injecting a second thermoplastic polymer into the second cavity, wherein the overmolding occurs at an interface between the layer and the ribbed structure,
wherein the interface is disposed on an outer portion of a rib including the microstructure, wherein the microstructure of the ribbed structure remains unfilled with the first thermoplastic polymer or the second thermoplastic polymer;
wherein the part has a Class A surface finish.

### Claim 2 (depends on 1)

The method of claim 1, wherein the ribs intrude into a portion of the layer creating an overlap between the ribbed structure and the layer or between the layer and the ribbed structure.

### Claim 3 (depends on 1)

The method of claim 1, wherein a depth of the overlap between the ribbed structure and the layer or between the layer and the ribbed structure at the respective overmolded portions is greater than or equal to 0.1 millimeter.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first thermoplastic polymer and the second thermoplastic polymer comprise a different polymer.

### Claim 5 (depends on 1)

The method of claim 1, wherein the first thermoplastic polymer or the second thermoplastic polymer comprises polybutylene terephthalate, acrylonitrile-butadiene-styrene, polycarbonate, polyethylene terephthalate, acrylic-styrene-acrylonitrile, acrylonitrile-(ethylene-polypropylene diamine modified)-styrene, phenylene ether resins, polyamides, phenylene sulfide resins, polyvinyl chloride, high impact polystyrene, polyolefins, polyimide, polypropylene, or a combination comprising at least one of the foregoing.

### Claim 6 (depends on 1)

The method of claim 1, wherein a diameter of each rib is greater than or equal to 1.5 millimeters.

### Claim 7 (depends on 1)

The method of claim 1, wherein a thickness of the layer is 0.5 millimeters to 50 millimeters.

### Claim 8 (depends on 1)

The method of claim 1, wherein a length of each rib is 5 millimeters to 100 millimeters.

### Claim 9 (depends on 1)

The method of claim 1, wherein a draft angle of each rib along a length of the rib is less than or equal to 5°.

### Claim 10 (depends on 1)

The method of claim 1, wherein the microstructure comprises a triangular cross-section.

### Claim 11 (depends on 1)

The method of claim 1, wherein a temperature of the first cavity is greater than the glass transition temperature of the first thermoplastic polymer and wherein the temperature of the second cavity is greater than the glass transition temperature of the second thermoplastic polymer or wherein a temperature of the bottom cavity is greater than the glass transition temperature of the first thermoplastic polymer and wherein the temperature of the top cavity is greater than the glass transition temperature of the second thermoplastic polymer.

### Claim 12 (depends on 1)

The method of claim 1, wherein a packing pressure of the first cavity or the second cavity is 25 MegaPascals to 1,000 MegaPascals.

### Claim 13 (depends on 1)

The method of claim 1, wherein warpage of the injection molded part is reduced as compared to an injection molded part made by a different process.

### Claim 14 (depends on 1)

The method of claim 1, further comprising:
forming a microchannel at the interface between the layer and the microstructure;
injecting a gas into the microchannel; and
enlarging the microchannel with the gas forming an open channel to reduce the amount of shrinkage experienced by the part.

### Claim 15 (depends on 1)

The method of claim 1, wherein
the thermoplastic polymer comprises a foaming agent.

### Claim 16 (depends on 15)

The method of claim 15, wherein
the foaming agent is at least one of carbon dioxide, sodium bicarbonate, azide compounds, ammonium carbonate, ammonium nitrite, monosodium citrate, light metals which evolve hydrogen upon reaction with water, chlorinated hydrocarbons, chlorofluorocarbons, azodicarbonamide, N,N′dinitrosopentamethylenetetramine, trichloromonofluoromethane, trichlorotrifluoroethane, methylene chloride, organic carboxylic acids, pentane, butane, ethanol, acetone, nitrogen gas (N2), and ammonia gas.