Patent US5648031A successfully refreshed from Google Patents.
US5648031A
Expired / Lapsed
US
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Method of forming antislip surfaces on thermoformed products
Assignee: Custom Plastics Molding Inc
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Filing: 1994-07-28
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Granted: 1997-07-15
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Expires: 2014-07-28
Abstract
Abstract A process for selectively forming an antislip surface on a product thermoformed from a plastic sheet is applied to truck bed liners, for example. The surface of the plastic sheet of HDPE or other thermoplastic material is cleaned and masked, to prepare a good molecular bonding surface on selected surface areas. A sprayable or liquid polymer selected to achieve desired characteristics of hardness and toughness without brittleness, such as a thermosetting elastomeric polymer, is formed into droplets, which are sprayed or otherwise applied onto the selected surface area. The droplets form a stippled pattern of primarily separate bumps across the selected surface area to be treated, occupying substantially less than 50% of the exposed area. After partial hardening of the bumps, the plastic sheet is thermoformed at thermoforming temperatures to produce the thermoformed product. Thermoforming tightly bonds the bumps or droplets to the thermoplastic sheet material, hardens the droplets forming macroscopic asperities, increases or enhances the three dimensional surface relief, and explodes some droplets with entrapped air to increase surface roughness.
Inventors
- 👤 Thomas M. Sturtevant
- 👤 Edward E. Cullivan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 11:23
CPC Classifications
B; B60; B60R; B60R13/00; B60R13/01; B05; B05D; B05D1/00; B05D1/02; B05D5/00; B05D5/02; B24; B24D; B24D3/00; B24D3/001; B24D3/002; B29; B29B; B29B11/00; B29B11/14; B29C; B29C49/00; B29C49/071; B29C51/00; B29C51/02; B29C2949/00; B29C2949/07; B29C2949/0715; B29C51/10; B29K; B29K2023/00; B29K2023/04; B29K2023/06; B29K2023/0608; B29K2023/065; B29K2995/00; B29K2995/0037; B29K2995/0072; B29L; B29L2031/00; B29L2031/30; B29L2031/3005; Y; Y10; Y10S; Y10S264/00; Y10S264/72; Y10T; Y10T428/00; Y10T428/23907; Y10T428/23957; Y10T428/24; Y10T428/24355; Y10T428/24372; Y10T428/2438; Y10T428/24405; Y10T428/25; Y10T428/254; Y10T428/29; Y10T428/2982; Y10T428/2991; Y10T428/2998
Claims Analysis
Total Claims: 63
Claim 1
Independent Claim
167 words
A process for selectively forming an antislip surface on a product thermoformed from a sheet comprising a thermoplastic material, the process comprising: forming droplets of a polymer; applying the droplets onto a selected surface area of the sheet to form on the sheet a stippled pattern of non-interconnected bumps of the polymer across the selected surface area leaving the sheet exposed between and completely around individual ones of the bumps; controlling the density of the droplets so that the bumps cover less than 50% of the selected surface area; at least partially hardening the bumps that have been formed on the sheet; and after the step of at least partially hardening the bumps, thermoforming the sheet at a thermoforming temperature, durably bonding the bumps to the sheet, and further hardening the bumps into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; wherein the polymer is selected so that the asperities have a hardness greater than the hardness of the sheet.
Claim 2
Dependent Claim
167 words
A process for selectively forming an antislip surface on a product thermoformed from a sheet comprising a thermoplastic material, the process comprising: forming droplets of a polymer; applying the droplets onto a selected surface area of the sheet to form on the sheet a stippled pattern of non-interconnected bumps of the polymer across the selected surface area leaving the sheet exposed between and completely around individual ones of the bumps; controlling the density of the droplets so that the bumps cover less than 50% of the selected surface area; at least partially hardening the bumps that have been formed on the sheet; and after the step of at least partially hardening the bumps, thermoforming the sheet at a thermoforming temperature, durably bonding the bumps to the sheet, and further hardening the bumps into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; wherein the polymer is selected so that the asperities have a hardness greater than the hardness of the sheet.
Claim 3
Dependent Claim
31 words
The process of claim 1, further comprising a step of cleaning the selected surface area of the sheet for removing contaminants and preparing a good molecular bonding surface on the sheet.
Claim 4
Dependent Claim
32 words
The process of claim 1, wherein the step of applying the droplets onto the sheet comprises flash spraying a mist of the droplets and depositing the mist onto the selected surface area.
Claim 5
Dependent Claim
33 words
The process of claim 3, further comprising masking the sheet so as to expose the selected surface area and cover other surface areas before the step of applying the droplets onto the sheet.
Claim 6
Dependent Claim
32 words
The process of claim 1, wherein the polymer is a thermosetting elastomeric polymer, and further comprising mixing an adhesion promoter with the thermosetting elastomeric polymer before the step of forming the droplets.
Claim 7
Dependent Claim
30 words
The process of claim 5, wherein the adhesion promoter is mixed with the thermosetting elastomeric polymer in the range of 1% by weight to 7% by weight of the mixture.
Claim 8
Dependent Claim
32 words
The process of claim 1, wherein the polymer is a thermosetting elastomeric polymer, and further comprising a step of mixing a polyurea prepolymer and an isocyanate to form the thermosetting elastomeric polymer.
Claim 9
Dependent Claim
20 words
The process of claim 1, wherein the polymer is selected so that the asperities on the product are not brittle.
Claim 10
Dependent Claim
21 words
The process of claim 1, wherein individual ones of the bumps have a substantially rounded domed shape protruding from the sheet.
Claim 11
Dependent Claim
18 words
The process of claim 1, wherein the sheet consists of one solid extruded layer of the thermoplastic material.
Claim 12
Dependent Claim
15 words
The process of claim 1, wherein the sheet comprises a layer of high density polyethylene.
Claim 13
Dependent Claim
23 words
The process of claim 1, wherein the sheet is substantially at room temperature when the step of applying the droplets is carried out.
Claim 14
Dependent Claim
35 words
The process of claim 1, wherein the step of thermoforming comprises vacuum forming the sheet into a vacuum mold such that a back side of the sheet opposite the selected surface area faces the mold.
Claim 15
Dependent Claim
217 words
A process for selectively forming an antislip surface on a product thermoformed from a sheet of plastic material comprising: cleaning a surface of the sheet for removing contaminants and preparing a good bonding surface; masking the sheet so as to expose a selected surface area to be provided with an antislip surface; forming into droplets a sprayable polymer; spraying a mist of the droplets and depositing the droplets onto the exposed selected surface area of the masked sheet, to form on the sheet a stippled pattern of primarily separate droplets without forming a continuous interconnected layer of the droplets across the selected surface area and while leaving the sheet substantially exposed between the droplets; controlling the time duration of the spraying so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets that have been deposited on the sheet to form the stippled pattern thereon; after the step of at least partially hardening the droplets, thermoforming the sheet at a thermoforming temperature, durably bonding the droplets to the sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; and selecting the polymer to have a hardness after thermoforming that is greater than the hardness of the sheet.
Claim 16
Dependent Claim
217 words
A process for selectively forming an antislip surface on a product thermoformed from a sheet of plastic material comprising: cleaning a surface of the sheet for removing contaminants and preparing a good bonding surface; masking the sheet so as to expose a selected surface area to be provided with an antislip surface; forming into droplets a sprayable polymer; spraying a mist of the droplets and depositing the droplets onto the exposed selected surface area of the masked sheet, to form on the sheet a stippled pattern of primarily separate droplets without forming a continuous interconnected layer of the droplets across the selected surface area and while leaving the sheet substantially exposed between the droplets; controlling the time duration of the spraying so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets that have been deposited on the sheet to form the stippled pattern thereon; after the step of at least partially hardening the droplets, thermoforming the sheet at a thermoforming temperature, durably bonding the droplets to the sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; and selecting the polymer to have a hardness after thermoforming that is greater than the hardness of the sheet.
Claim 17
Dependent Claim
29 words
The process of claim 14, wherein the step of cleaning the surface of the sheet comprises flame treatment for burning off contaminants and preparing a good molecular bonding surface.
Claim 18
Dependent Claim
23 words
The process of claim 14, wherein the steps of forming the droplets and spraying the mist are accomplished using a mixing spray head.
Claim 19
Dependent Claim
22 words
The process of claim 14, wherein the polymer comprises a thermosetting elastomeric polymer formed by mixing a polyurea prepolymer with an isocyanate.
Claim 20
Dependent Claim
11 words
The process of claim 17, wherein the isocyanate is diphenylmethane-4 4'diisocyanate.
Claim 21
Dependent Claim
14 words
The process of claim 14, wherein the polymer is a hybrid polyurea polyurethane polymer.
Claim 22
Dependent Claim
19 words
The process of claim 14, wherein the thermoforming temperature is in a range of 250° F. to 550° F.
Claim 23
Dependent Claim
32 words
The process of claim 14, wherein the product is a truck bed liner and the selected surface area corresponds to a portion of a cargo carrying surface of the truck bed liner.
Claim 24
Dependent Claim
40 words
The process of claim 16, further comprising controlling the time duration of the spraying to a fraction of a second, and setting the spray pressure from the spray head to a pressure in the range of 1000 to 2000 lbs.
Claim 25
Dependent Claim
31 words
The process of claim 22, wherein the step of spraying is carried out from the spray head arranged at a distance from the sheet in the range of 2.5' to 4.5'.
Claim 26
Dependent Claim
29 words
The process of claim 14, wherein the polymer is a thermosetting elastomeric polymer and the droplets are formed in the diameter size range of 2 mils to 30 mils.
Claim 27
Dependent Claim
25 words
The processing claim 14, wherein the polymer is a thermosetting elastomeric resin with a reaction time in the range of several seconds to 30 seconds.
Claim 28
Dependent Claim
30 words
The process of claim 14, wherein the polymer is a thermosetting elastomeric resin, and further comprising mixing an adhesion promoter with the polymer before the step of forming the droplets.
Claim 29
Dependent Claim
27 words
The process of claim 26, wherein the adhesion promoter is mixed with the thermosetting elastomeric resin to the extent of approximately 5% by weight of the mixture.
Claim 30
Dependent Claim
224 words
A process for selectively forming an antislip surface on a cargo carrying surface portion of a truck bed liner thermoformed from a sheet of high density polyethylene (HDPE) comprising: cleaning at least a selected surface area of the sheet that is to be provided with the antislip surface, for removing contaminants, exposing the HDPE, and preparing a good molecular bonding surface; masking the sheet while leaving the selected surface area exposed; forming into droplets a thermosetting elastomeric polymer; spraying and depositing a mist of the droplets onto the exposed surface area of the sheet, and forming on the sheet a stippled pattern of primarily separate droplets without forming a continuous interconnected layer of the droplets across the selected surface area and while leaving the sheet substantially exposed between droplets; controlling the time duration of the spraying so that said droplets occupy substantially less than 50% of the selected surface area; carrying out an initial curing step for at least partially hardening the droplets that have been deposited on the sheet to form the stippled pattern thereon; and, after the initial curing step, thermoforming the sheet in a thermoforming temperature range of 250° F. to 550° F., durably bonding the droplets to the sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area.
Claim 31
Dependent Claim
224 words
A process for selectively forming an antislip surface on a cargo carrying surface portion of a truck bed liner thermoformed from a sheet of high density polyethylene (HDPE) comprising: cleaning at least a selected surface area of the sheet that is to be provided with the antislip surface, for removing contaminants, exposing the HDPE, and preparing a good molecular bonding surface; masking the sheet while leaving the selected surface area exposed; forming into droplets a thermosetting elastomeric polymer; spraying and depositing a mist of the droplets onto the exposed surface area of the sheet, and forming on the sheet a stippled pattern of primarily separate droplets without forming a continuous interconnected layer of the droplets across the selected surface area and while leaving the sheet substantially exposed between droplets; controlling the time duration of the spraying so that said droplets occupy substantially less than 50% of the selected surface area; carrying out an initial curing step for at least partially hardening the droplets that have been deposited on the sheet to form the stippled pattern thereon; and, after the initial curing step, thermoforming the sheet in a thermoforming temperature range of 250° F. to 550° F., durably bonding the droplets to the sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area.
Claim 32
Dependent Claim
20 words
The process of claim 28, wherein the thermosetting elastomeric polymer is formed by mixing a polyurea prepolymer with an isocyanate.
Claim 33
Dependent Claim
16 words
The process of claim 28, wherein the thermosetting elastomeric polymer is a hybrid polyurea polyurethane polymer.
Claim 34
Dependent Claim
55 words
The process of claim 28, wherein the time duration of the spraying is controlled to a fraction of a second, and the spraying is carried out through a spray head at a pressure in the range of 1000 to 2000 lbs, and at a distance from the sheet in the range of 2.5' to 4.5'.
Claim 35
Dependent Claim
58 words
The process of claim 28, wherein the step of cleaning the sheet comprises flame treatment to burn off contaminants and prepare a good bonding surface, wherein the step of at least partially hardening the droplets comprises using heat and air, and wherein the thermoforming is carried out in a thermoforming temperature range of 370° F. to 400° F.
Claim 36
Dependent Claim
32 words
The process of claim 28, wherein the step of forming the thermosetting elastomeric polymer into droplets comprises forming the droplets in the size range of 2 mils to 30 mils in diameter.
Claim 37
Dependent Claim
22 words
The process of claim 28, wherein the droplets after thermoforming are substantially in the size range of 2 mils to 30 mils.
Claim 38
Dependent Claim
23 words
The process of claim 28, wherein the thermosetting elastomeric polymer has a reaction time in the range of several seconds to 30 seconds.
Claim 39
Dependent Claim
43 words
The process of claim 28, further comprising entrapping air in at least some of the droplets and exploding the entrapped air through the top of the droplets during the thermoforming, thereby forming rough edges on the droplets to increase the coefficient of friction.
Claim 40
Dependent Claim
23 words
The process of claim 28, further comprising mixing an adhesion promoter with the thermosetting elastomeric polymer before the step of forming the droplets.
Claim 41
Dependent Claim
30 words
The process of claim 37, wherein the adhesion promoter is mixed with the thermosetting elastomeric polymer in the range of 1% by weight to 7% by weight of the mixture.
Claim 42
Dependent Claim
158 words
A process for selectively forming an antislip surface on a product thermoformed from a plastic sheet of thermoplastic material comprising: mixing a polyurea prepolymer and an isocyanate to form a thermosetting elastomeric polymer; forming droplets of the polymer; applying the droplets onto the plastic sheet over a selected surface area, and forming a stippled pattern of primarily separate droplets across the selected surface area leaving the plastic sheet substantially exposed between droplets; controlling the density of the droplets so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets forming the stippled pattern; and thermoforming the plastic sheet at a thermoforming temperature, durably bonding the droplets to the plastic sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; wherein the polymer is selected to have a hardness after thermoforming greater than the hardness of the plastic sheet.
Claim 43
Dependent Claim
158 words
A process for selectively forming an antislip surface on a product thermoformed from a plastic sheet of thermoplastic material comprising: mixing a polyurea prepolymer and an isocyanate to form a thermosetting elastomeric polymer; forming droplets of the polymer; applying the droplets onto the plastic sheet over a selected surface area, and forming a stippled pattern of primarily separate droplets across the selected surface area leaving the plastic sheet substantially exposed between droplets; controlling the density of the droplets so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets forming the stippled pattern; and thermoforming the plastic sheet at a thermoforming temperature, durably bonding the droplets to the plastic sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; wherein the polymer is selected to have a hardness after thermoforming greater than the hardness of the plastic sheet.
Claim 44
Dependent Claim
11 words
The process of claim 39, wherein the isocyanate is diphenylmethane-4 4'diisocyanate.
Claim 45
Dependent Claim
148 words
A process for selectively forming an antislip surface on a product thermoformed from a plastic sheet of thermoplastic material comprising: forming droplets of a hybrid polyurea polyurethane polymer; applying the droplets onto the plastic sheet over a selected surface area, and forming a stippled pattern of primarily separate droplets across the selected surface area leaving the plastic sheet substantially exposed between droplets; controlling the density of the droplets so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets forming the stippled pattern; and thermoforming the plastic sheet at a thermoforming temperature, durably bonding the droplets to the plastic sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; wherein the polymer is selected to have a hardness after thermoforming greater than the hardness of the plastic sheet.
Claim 46
Dependent Claim
148 words
A process for selectively forming an antislip surface on a product thermoformed from a plastic sheet of thermoplastic material comprising: forming droplets of a hybrid polyurea polyurethane polymer; applying the droplets onto the plastic sheet over a selected surface area, and forming a stippled pattern of primarily separate droplets across the selected surface area leaving the plastic sheet substantially exposed between droplets; controlling the density of the droplets so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets forming the stippled pattern; and thermoforming the plastic sheet at a thermoforming temperature, durably bonding the droplets to the plastic sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; wherein the polymer is selected to have a hardness after thermoforming greater than the hardness of the plastic sheet.
Claim 47
Dependent Claim
180 words
A process for selectively forming an antislip surface on a product thermoformed from a plastic sheet of thermoplastic material comprising: forming droplets of a liquid polymer; applying the droplets onto the plastic sheet over a selected surface area, and forming a stippled pattern of primarily separate droplets across the selected surface area leaving the plastic sheet substantially exposed between droplets; controlling the density of the droplets so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets forming the stippled pattern; thermoforming the plastic sheet at a thermoforming temperature, durably bonding the droplets to the plastic sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; and entrapping air in at least some of the droplets and exploding the entrapped air out through the droplets during the thermoforming, thereby forming rough edges on the droplets to increase the coefficient of friction; wherein the polymer is selected to have a hardness after thermoforming greater than the hardness of the plastic sheet.
Claim 48
Dependent Claim
180 words
A process for selectively forming an antislip surface on a product thermoformed from a plastic sheet of thermoplastic material comprising: forming droplets of a liquid polymer; applying the droplets onto the plastic sheet over a selected surface area, and forming a stippled pattern of primarily separate droplets across the selected surface area leaving the plastic sheet substantially exposed between droplets; controlling the density of the droplets so that the droplets cover less than 50% of the selected surface area; at least partially hardening the droplets forming the stippled pattern; thermoforming the plastic sheet at a thermoforming temperature, durably bonding the droplets to the plastic sheet, and further hardening the droplets into tough macroscopic asperities causing a relatively higher coefficient of friction over the selected surface area; and entrapping air in at least some of the droplets and exploding the entrapped air out through the droplets during the thermoforming, thereby forming rough edges on the droplets to increase the coefficient of friction; wherein the polymer is selected to have a hardness after thermoforming greater than the hardness of the plastic sheet.
Claim 49
Independent Claim
177 words
A method for providing an antislip surface on at least a selected surface area of a thermoformed product, comprising the following steps in sequence: (a) providing a base sheet comprising a layer of a first polymer; (b) applying a plurality of individual non-interconnected islands comprising a second polymer onto at least a selected surface area of said base sheet, so that said islands cover less than 50% of said selected surface area; (c) at least partially hardening said second polymer of said islands; (d) heating said base sheet; and (e) thermoforming said base sheet at a thermoforming temperature to form said thermoformed product by applying an air pressure differential across said base sheet in a mold, so as to bring a back side of said base sheet opposite said selected surface area into contact with a mold surface of said mold; wherein after said step (e), said islands provide an increased coefficient of friction greater than a coefficient of friction of said base sheet, and said selected surface area with said islands thereon forms said antislip surface.
Claim 50
Independent Claim
177 words
A method for providing an antislip surface on at least a selected surface area of a thermoformed product, comprising the following steps in sequence: (a) providing a base sheet comprising a layer of a first polymer; (b) applying a plurality of individual non-interconnected islands comprising a second polymer onto at least a selected surface area of said base sheet, so that said islands cover less than 50% of said selected surface area; (c) at least partially hardening said second polymer of said islands; (d) heating said base sheet; and (e) thermoforming said base sheet at a thermoforming temperature to form said thermoformed product by applying an air pressure differential across said base sheet in a mold, so as to bring a back side of said base sheet opposite said selected surface area into contact with a mold surface of said mold; wherein after said step (e), said islands provide an increased coefficient of friction greater than a coefficient of friction of said base sheet, and said selected surface area with said islands thereon forms said antislip surface.
Claim 51
Dependent Claim
16 words
The method of claim 43, wherein said first polymer and said second polymer are different polymers.
Claim 52
Dependent Claim
22 words
The method of claim 43, wherein said first polymer is a thermoplastic polymer, and said second polymer is a thermosetting elastomeric polymer.
Claim 53
Dependent Claim
19 words
The method of claim 43, further comprising preparing said second polymer by mixing a polyurea prepolymer and an isocyanate.
Claim 54
Dependent Claim
20 words
The method of claim 43, wherein said second polymer is a hybrid polyurea polyurethane polymer in which the polyurea predominates.
Claim 55
Dependent Claim
43 words
The method of claim 43, wherein said step (b) comprises applying discrete droplets comprising said second polymer onto said selected surface area of said base sheet, and wherein substantially each of said islands is a discrete rounded bump protruding from said base sheet.
Claim 56
Dependent Claim
39 words
The method of claim 43, wherein said steps (d) and (e) together are carried out so as to increase a projection height of said islands above said base sheet after said step (e) compared with before said step (d).
Claim 57
Dependent Claim
56 words
The method of claim 43, wherein said steps (d) and (e) together are carried out so as to further harden said second polymer of said islands, to durably bond said islands onto said base sheet, and to form of said islands tough macroscopic asperities that provide said increased coefficient of friction over said selected surface area.
Claim 58
Dependent Claim
26 words
The method of claim 43, further comprising selecting said second polymer so that said second polymer is harder than said first polymer after said step (e).
Claim 59
Dependent Claim
27 words
The method of claim 43, wherein said first polymer is high density polyethylene, and wherein said base sheet consists of one layer of said high density polyethylene.
Claim 60
Dependent Claim
18 words
The method of claim 43, wherein said step (a) comprises providing said base sheet substantially at room temperature.
Claim 61
Dependent Claim
47 words
The method of claim 43, wherein said base sheet has a thickness in the range from 180 mils to 250 mils, and wherein said first polymer and said thickness of said base sheet are selected so that after said step (e) said base sheet is substantially form-stable.
Claim 62
Independent Claim
168 words
A method for providing an antislip surface on at least a selected surface area of a thermoformed product, comprising the following steps in sequence: (a) providing a base sheet comprising a layer of a first polymer; (d) applying a plurality of individual non-interconnected islands comprising a second polymer onto at least a selected surface area of said base sheet, so that said islands cover less than 50% of said selected surface area; (c) at least partially hardening said second polymer of said islands; (d) heating said base sheet; and (e) thermoforming said base sheet at a thermoforming temperature by applying an air pressure differential across said base sheet in a mold, so as to bring a back side of said base sheet opposite said selected surface area into contact with a mold surface of said mold; further comprising entrapping gas in at least some of said islands, and bursting open said gas-entrapping islands by expanding said entrapped gas during at least one of said steps (d) and (e).
Claim 63
Independent Claim
168 words
A method for providing an antislip surface on at least a selected surface area of a thermoformed product, comprising the following steps in sequence: (a) providing a base sheet comprising a layer of a first polymer; (d) applying a plurality of individual non-interconnected islands comprising a second polymer onto at least a selected surface area of said base sheet, so that said islands cover less than 50% of said selected surface area; (c) at least partially hardening said second polymer of said islands; (d) heating said base sheet; and (e) thermoforming said base sheet at a thermoforming temperature by applying an air pressure differential across said base sheet in a mold, so as to bring a back side of said base sheet opposite said selected surface area into contact with a mold surface of said mold; further comprising entrapping gas in at least some of said islands, and bursting open said gas-entrapping islands by expanding said entrapped gas during at least one of said steps (d) and (e).
References Cited (Backward Citations)
US73919A
Cited
US1411912A
Cited
US1657687A
Cited
US2120406A
Cited
US2576290A
Cited
US2793136A
Cited
GB850791A
Cited
US3148103A
Cited
US3124807A
Cited
US3450563A
Cited
US3598677A
Cited
US3573155A
Cited
US3629051A
Cited
US3629380A
Cited
US4329312A
Cited
US3878147A
Cited
US4109041A
Cited
US4196259A
Cited
US4488918A
Cited
US4420513A
Cited
US4614686A
Cited
US4592583A
Cited
US4693507A
Cited
US4692370A
Cited
US4721641A
Cited
US4760103A
Cited
US4745139A
Cited
US5053253A
Cited
US5094902A
Cited
US5110657A
Cited
US5194194A
Cited
US5263761A
Cited
USPTO Annuity & Maintenance Windows
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| 7.5 Years (Year 8) | 2004-07-14 | 2005-01-13 | 2005-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-07-14 | 2009-01-13 | 2009-07-15 | $7700.00 | Window Closed / Lapsed |