CA1107625A

CA1107625A - Chemical resistant decorative laminate

Info

Publication number: CA1107625A
Application number: CA284,408A
Authority: CA
Inventors: William L. Lindamood; Jerry L. Malina; Gerald J. Bruckbauer; Melvin Pitts; Earl J. Soudelier; Glenn L. Odstrcil; James H. Jones; Ray E. Schiller
Original assignee: Dart Industries Inc
Current assignee: Dart Industries Inc
Priority date: 1976-09-02
Filing date: 1977-08-10
Publication date: 1981-08-25
Also published as: FR2363437A1; IE45461L; GT197748022A; JPS5331777A; DE2739211A1; AR212725A1; IE45461B1; MX147055A; NZ184929A; IL52689A; GB1582473A; BR7705773A; AU498588B2; IN147245B; DE2739211C2; IL52689A0; BE858285A; DK389777A; NL172423C; SE7709864L

Abstract

ABSTRACT OF THE DISCLOSURE

A process is disclosed for producing a decorative laminate which comprises applying a polyester resin to a decorative sheet, curing the resin, preparing an assembly of superimposed sheets by placing the decorative sheet upon a dry sheet, placing beneath the dry sheet a plurality of thermosetting resins impregnated sheets and consolidating the assembly under heat and pressure to form a unitary laminated structure. The high pressure decorative laminate obtained has exceptional stain and chemical resistant properties.

Description

BACXGROUND OF THE INVENTION
-The present invention relates to cured resin products formed by lamination techniques. In one aspect of the invention a chemically resistant laminate is formed by consolidating discrete layers of materials under heat and pressure. Another aspect of the invention concerns the method and order of laying-up pre-determined discrete layers for subsequent lamination.

DESCRIPTION OF THE PRIOR ART
Countertops for all types of laboratories, beauty shops, pharmacies, and other commercial applications must be stain and chemical resistant in addition to being wear and impact resistant.
Typically such countertops are constructed of slate, marble, composition stone, or black or gray colored wood surfaces covered with a varnish. Of course, the slate and marble are heavy, difficult to install, and expensive. The painted w03d counters are readily scra~ched or abraded and require frequent maintenance., Surfaces coated with a cured polyester resin have exceptional chemical resistance properties, and are also wear resistant.
However, unless such surfaces are bonded to a high density SUD-strate or the like, they will lack impact strength and are not as durable. Melamine/formaldehyde resin laminates provide a good wear and impact resistant surface which can also be decora-tive but lack the ability to resist chemical attack.

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An attempt to overcome this problem is shown in U.S. Patent 3,756,901 wherein a fiberglass sheet and a heavy kraft paper are impregnated with polyester resins to produce a low pressure laminate. The kraft paper must have a basic weight of greater than l40 pounds to produce a laminate having adequate impact resistance.
U.S. Patent 3,929,545 to E.J. Van Dyck et al discloses a similar low pressure polyester laminate, but this product is generally suitable for vertical applications where impact and wear resistance are not factors.
U.S. Patent 3,551,241 discloses a lay-up comprising core-stock impregnated with phenolic resin, a decorative sheet impreg-nated with melamine/formaldehyde resin, and a top release sheet coated with polyester resin. The lay-up is consolidated under high temperature and pressure conditions. Of course, the final product is a strong rigid laminate but lacks wear resistance and suffers delamination defects because of the immiscibility and resultant lack of good bond between a polyester resin and a melamine/formaldehyde resin.

SUMMARY OF THE INVENTION
The present invention provides a laminated product and method therefor which can offer decorati~e patterns and/or color choices in combination with exceptional chemical and stain resistance. The product is a high pressure laminate wherein the desirable properties of transparency, chemical resistance and wear resistance produced with a polyester resin surface layer are synergistically combined with the desirable strengthening features of melamine and phenolic resin impregnated substrate layers. The immiscibility and delamination defects common in prior art laminations are overcome with the use of an interme-diate dry sheet between the polyester resin layers and the 76~i melamine (melamine/formaldehyde)and/or phenolic resin impregnated substrate layers. During lamination, each of the respective resins on opposite sides of the dry sheet penetrate therein a certain distance. In this manner, the immiscible resins are integrally bound together with the dry sheet to form a unitary final product having the combined desirable features of both resin systems. Alternatively, it is envisaged that a partially impregnated decorative sheet having a dry surface in contast with the melamine and/or phenolic resin impregnated substrate layers would a]so function to bond the immiscible resin layers together.
Thus, in accordance with the present teachings, a process is provided for producing a decorative laminate which comprises applying a polyester resin to a decorative sheet and curing the resin. An assembly is prepared of superimposed sheets by placing the decorative sheet upon a dry sheet and placing beneath the dry sheet a plurality of -thermosetting resin im-pregnated sheets and consolidating the assembly under heat and pressure to a unitary laminated structure.
DESCRIPTION OF PREFERRED EMBODIMENTS
In accordance with the present invention, it will be seen that unique procedures are utilized to produce high pressure laminates having properties that were hitherto un-ayailable in a single product. In a first -technique, a release sheet that has been coated with a "B" staged polyester resin is placed upon a polyester impregnated decorative sheet. The decorative sheet is placed upon a dry sheet: For example, a sheet of paper which has not been subjected to a treating or coating procedure. This assembly is then consolidated under heat and pressure with various types of thermosetting resin _3_ ~ ~ .

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impregnated substrate sheets. At the conclusion of the consolidation step, the release sheet is removed.
To describe the procedure in more detail, the first technique calls for the use of a flexible release sheet upon which is applied a polyester resin film. The release sheet may be anyone of a plurality of commonly used materials such as cellophane, polyester film, aluminum foil, or foil-paper laminates Additionally, papers which have been coated or treated with polyethylene, polypropylene, polyfluorocarbon lQ

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material~, silicone, or other release materials may be utilized to enhance the release of the film from the sheet. It will also be appreciated that the release sheet may be textured so that it can impart an embossed surface finish to the surface of the finished laminate.
The polyester resin used for coating the release sheet consists of about 100% reactive solids. Particular polyester resin mixtures may be found in U.S. Patent 3,756,901.
Apparatus suitable for use in curing the resin to a semisolid "B" stage may be found in U.S. Patent 3,929,545 Generally, the resin contains about 65% polyester resin and 35% styrene monomer. These components are mixed with photoinitiators or ~.V.
light sensitizers and peroxide and are applied to the release sheet by conventional reverse roll coating apparatus. The film thickness is generally controlled between about 5 and 20 mils.
The coated sheet is passed through an ultraviolet light processor wherein U.V. light operates to cure the resin to a semisolid state.
The speed of the coated sheet through the processor and the number of U.V. lamps and distance from the sheet are important variables in achieving the semi-cured non-mobil~film referred to as a "B"
stage cure. As the coated release sheet exits the processor, the partially cured film is interleafed with a polyethylene film for temporary storage prior to its use in the aforementioned lay-up.
The decorative sheet used with the present invention is saturated to contain from 40-63% resin solids and preferably between about 48 and 52%. To achieve this, a polyester resin mixture is prepared containing about 85-35% resin and 5-15~
vinyl monomer. To this mixture is added catalysts, inhibitors, and silica materials to control the melt viscosity and flow characteristics oE the fluid. A viscosity between 150 and 500 centipoise is produced by adding a solvent such as acetone ~$7~i~3 and/or methyl ethyl ketone.
The decorative sheet is fed into a vat containing the solvent resin system, and the amount of resin applied to the sheet is controlled by feeding the wetted sheet through metering rolls.
The impregnated sheet is dried in a heated oven to remove a substantial portion of the volatile solvents. Generally, the dried sheet should not contain more than between 4 and 6%
volatiles. As the sheet exits from the drying oven~ it is cooled and interleafed with a plastic film and wound on a continuous roll for temporary storage until further processing into a final laminated product.
A final laminate assembly is prepared by arranging in a stacked relationship a plurality of substrate materials which have been impregnated with a thermosetting resin. Over the sub-strate is placed an overlay that has been impregnated with a thermosetting resin such as melamine. This overlay may be in fact a barrier sheet depending upon the color and/or type o~
sheet being utilized.
Above the barrier and/or melamine treated overlay is a dry sheet, and immediately above the dry sheet is the polyester impregnated decorative sheet. The coated release sheet is placed upon the impregnated decorative sheet with the "B"
staged polyester coating in direct contact with the decorative sheet. The entire assembly is placed into a conventional laminating press and is heat and pressure consolidated to a final unitary laminated structure. The pressure is generally from 800-1200 PSI with a temperature range of about 225-325~.
The overall thickness of the final laminate product produced by the above-described technique can be controlled by the number of layers of substrates used.
A second techni~ue for producing the chemically resistant high pressure laminate of the present invention involves the ~ .7 ~

direct coating o~ dry decorative paper with a thermosetting polyester resin. The coated resin is "B" staged to a semisolid state and subsequently bon~ed to various substrate materials as described in the first technique. This method has the advantage of combining the steps of resin coating the release sheet and "B" staging of the release sheet as well as the impregnation and drying operation used to produce the previously described impregnated decorative sheet.
In particular, the second technique involves the reverse roll coating of a decorative sheet with a heat curable polyester resin of the type used for coating the release sheet. In this instance, however, the coating thickness is increased to about 11-30 mils. The coating is cured through the U.V. processor in the same manner as that described with the release sheet. Upon exiting the processor, the partially cured polyester film is interleafed with a plastic sheet and wound into rolls for temporary storage, or it can be immediately cut into sheets for use in the lay-up of a final laminate.
It will be appreciated that upon application of the polyester film to the surface of the decorative sheet7 a portion of the resin will penetrate the sur-face of ~he sheet.
Generally, the preferred resin content is between 75 and 85% of the total weight of the sheet with a volatile content of between 2 and 6%. A laminate assembly based upon the second technique is prepared by placing, in a stacked rela-tionship, a plurality of resin treated substrate materials above which is placed a resin treated barrier or overlay sheet. Over the barrier sheet is placed a dry intermediate sheet and the polyester coated and impregnated sheet is placed upon this. The entire assembly is consolidated as previously described in a conventional high pressure lamina-ting press.

To achie~e a more complete understanding of the present invention, the following examples are set forth. It will be appreciated, however, that these examples are primari-ly for the purpose of illumination and/or illustration and specific details contained therein should not be interpreted as a limitation on the invention~

An isophthalic polyester resin is prepared containing 88.7~ Ashland Chemical Company's 7200 polyester resin and 11.3% vinyl monomer (diallyl phthalate). To this is added:
1% t-butyl perbenzoate, 1% benzoyl peroxide, 250 PPM (.025%) BHT inhibitor, and 3.77% Cab-O-Sil M5 (Cabot Corporation) fumed silica. These ingredients are added to a solvent blend of acetone and methyl ethyl ketone in a proportion resulting in a final viscosity between 150-500 centipoise.
A decorative alpha cellulose sheet is fed under tension into a vat containing the above-described resin and passed between metering rolls which control the resin content in the paper. The saturated sheet is then force air dried in a steam heated oven containing graduated temperature ~ones.
The amount of rolatiles in the exiting sheet is controlled between 4 and 6%, whereas the resin solids as a portion of the to~al impregnated sheet is controlled between 48 and 52%.
The exiting sheet is cooled and interleafed with polyethylene film and wound into a continuous roll.
An aluminum foil release sheet is coated with a polyester resin consisting of Ashland Chemical Company's 7200 resin in styrene ~65% alkyd., 35% styrene). To these reactive solids are added 1% photoinitiator, Triganol 14 (Noury Chemical Compa~y), 0.75% t-butyl perbenzoate, 800 PPM (.08%) Pluronic L122 surfactant (BASF Wyandotte Corporation) and 500 PPM

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C.05%) BHT inhibitor. The aluminum foil release sheet is passed over a reverse direction roll coater. A layer of the above-described polyester resin controlled at a film thick-ness of about 12-14 mils ;s applied. The coated release sheet is then passed through a U.V. processor in which ultraviolet light is emitted from 200 watts per inch mercury vapor lamps operating at 1500 volts and 7.5 amps. The line speed is about 8 feet per minute per lamp with the lamps about 6 inches above the film. Upon exiting the U.V. processor, the "B" staged cured polyester film is interleafed with a polyethylene film and wound into a roll for storage.
Predetermined lengths of the coated release sheet and decorative laminate are layed-up with resin impregnated substrate sheets in a conventional laminating press and consolidated between 800-1200 PSI and 270-312F for about 35 minutes.
The laminate is cooled for about 25 minutes and removed from the press.
The following order of lay-up produced a unitary laminate structure which exhibited physical properties in excess of comparable NEMA standard values with a chemical and stain resistance which far exceeded conventional melamine-formaldehyde high pressure laminates:

Polyester coated and U.V. "si~ staged release sheet Polyester Pre-Preg 50% resin content Dry overlay ~elamine treated barrier 40-50~ resin content ll-Phenolic treated kraft paper 35-38~ resin 122# basis wt.
Melamine treated overlay - 70% resin content Example 1 is repeated except that the lay-up is:

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Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg 50% resin content Dry overlay Melamine treated overlay - 70~ resin content ll-Phenolic treated kraft paper 34-38% resin content 122# basis wt Melamine treated overlay - 70% resin content Example 1 is repeated except that the lay-up is:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg 50% resin content Polyester barrier sheet 40-50% resin content Dry overlay Melamine treated overlay - 70% resin content ll-Phenolic treated kraft paper 34-38% resin 122~ basic wt, Melamine treated overlay - 70~ resin content Example 1 is repeated except that the lay-up is:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg 50% resin content Dryibarrier Me~amine treated overlay - 70% resin content ll-Phenolic treated kraft paper 34-38~ resin 122# basic wt.
Melamine treated overlay - 70% resin content - Example 1 is repeated except that the lay-up is:
Polyester coated and U.V~ "B" staged release sheet Polyester Pre-Preg 50% resin content Dry overlay Melamine treated barrier 40-50% resin content 3-Phenolic treated kraft paper 40% resin content 132# basis wt.
Dxy crepe Dry overlay Example 1 is repeated except that the lay-up is:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg 50% resin content Dry overlay Melamine treated overlay - 70% resin content 3-Phenolic treated kraft paper 40% resin content 132# basis wt.
Dry crepe Dry overlay Example 1 is repeated except that the lay-up is:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg 50% resin content Polyester barrier sheet 40-50% resin content Dry overlay Melamine treated overlay - 70% resin content 3-Phenolic treated kraft paper 40~ resin content 132# basis wt.
Dry crepe Dry overlay EXAMPLE B
Example 1 is repeated except that the lay-up is:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg 50% resin content Dry barrier Melamine treated overlay 70% resin content 3-Phenolic treated kraft paper 40% resin content 132# basis wt.
Dry crepe Dry overlay An example of a laminate produced by the second technique is as follows:
An isophthalic polyester resin solution having a viscosity 7~

between 1000 and 2000 centipoise is prepared consisting of Ashland Chemical Company's 7220 resin, 1% triganol 14 ~NOUTY
Chemical Company), 0.75~ t-butyl perbenzoate, 800 PPM (.08~) pluronic surfactant tBASF Wyandotte Corporation) and 500 PPM
(.05%) BHT inhibitor. A decorative alpha cellulose sheet is passed over a reverse direction roll coater containing the above-described resin and wherein a film thickness of approximately 17-20 mils is applied. The speed of the coater is controlled so that a small amount of saturation of the resin in the sheet takes place during the time the sheet travels the distance between the roll coater and curing source. "B" stage curing is accomplished with the U.V. processoT described in Example 1.
The "B" staged decorative sheet may be interleafed with a polyethylene sheet and rolled for storage or it may be immediately cut into predetermined lengths and processed into a decorative laminate.
The procedure is to form an assembly by superimposing ~he polyester resin impregnated decorative sheet with resin impreg-nated substrate materials as follows:
W coated pattern paper 75-85% resin content DTY overlay Melamine treated barrier 40 50~ resin content ll-Phenolic treated kraft paper 34-38~ resin content 122#
basis wt.
Melamine treated overlay - 70% resin content The above lay-up is consolidated into a unitary structure as described in Example 1. The laminate structure exhibited physical properties in excess of comparable NEMA standard values with a chemical and stain resistance which far exceeded conventional melamine-formaldehyde high pTessure laminates.

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The technique of Example 9 is repeated except that the lay-up is:
UV coated pattern paper 75-85% resin content Polyester barrier sheet 40-50~ resin content Dry overlay Melamine treated barrier 40-50% resin content ll-Phenolic treated kraft paper 34-38% resin content 122# basis wt.
Melamine treated overlay - 70% resin content The techni~ue of Example 9 is repeated except that the lay-up is:
W coated pattern paper 75-85% resin content Dry overlay Melamine treated overlay - 70% resin content ll-Phenolic treated kraft paper 34-38% resin content 122# basis wt, Melamine treated overlay - 70% resin content The technique of Example 9 is repeated except that the lay-up is:
W coated pattern paper 75-85% resin content Polyester barrier sheet 40-50% resin content Dry overlay Melamine treated overlay - 70% resin content ll-Phenolic treated kraft paper 34-38% resin content 122# basis wt.
Melamine treated overlay - 70% resin content ~XAMPLE 13 The technique of Example 9 is repeated except that the lay-up is:
W coated pattern paper 75-85% resin content Dry overlay Melamine treated barrier 40-50% resin con-tent 3-Phenolic treated kraft paper 40% resin content 132# basis wt.
Dry crepe Dry overlay The technique of Example 9 is repeated except that the lay-up is:
UV coated pattern paper 75-85% resin content Polyester barrier sheet 40-50% resin content Dry overlay Melamine treated barrier 40-50% resin content 3-Phenolic treated kraft paper 40% resin content 132# basis wt.
Dry crepe Dry overlay The technique of Example 9 is repeated except that the lay-up is:
UV coated pattern paper 75-85~ resin content Dry overlay Melamine treated overlay 70% resin content 3-Phenolic treated kraft paper 40% resin content 132# basis wt.
Dry crepe Dry overlay

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The technique of Example 9 is repeated excep~ that the lay-up is.
UV coated pattern paper 75-85~ resin content Polyester barrier 40-50% resin content Dry overlay Melamine treated overlay 70% resin content

3-Phenolic treated krat paper 40% resin content 132# basis wt.
Dry crepe Dry overlay A third technique for producing the laminate of the-present invention concerns the use of a decorative sheet partially impregnated with polyester resin. The decorative sheet will be coated on its face side with the polyester resin.
Impregnation will occur with resin penetration into the sheet a distance less than its full thickness. The sheet will be layed-up with its back dry side in contact with melamine-formaldehyde resin impregnated overlay or barrier sheet layers.
During lamination the melamine-formaldehyde resin will migrate into the dry portion of the decorative sheet thereby forming a bond with the polyester impregnated portion of the decorative sheet.
It will be understood that the polyester resin formulations may be the same as those set forth in Examples l and 9 above.
It is desirable, however, to adjust the viscosity of the polyester resin to a level above 300 centipoise to inhibit the complete saturation of the decorative sheet. Preferred viscosity range adjustments of 300-3000 centipoise are readily affected by the amount o~ solvents and/or thixotropic agents utilized.
It will also be appreciated that impregnation of the decorative paper is affected by the basis weight, thickness, surface finish porosity and/or saturation characteristics 7~2~
Lnereof. Additional factors are the speed through the curing o~en or U.V. processor whereby the slower the speed, the more time the resin will have to penetrate the paper fibrous structure. Of course, the melamine-formaldehyde impregnated sheet will have sufficient resin to flow into the dry portion of the decorative sheet. A 35-55% resin content range will usually be sufficient.

An example of a laminate produced by the third technique is as follows:
An isophthalic polyester resin is prepared containing 88.7~ Ashland Chemical Company's 7200 polyester resin and 11.3~ vinyl monomer (diallyl phthalate). To this is added:
1~ t-butyl perbenzoate, 1% benzoyl peroxide, 250 PPM (.025%) BHT inhibitor, and 4.8% Cab-O-~il M5 (Cabot Corporation) fumed silica. These ingredients are added to a solvent blend of ~cetone and methyl ethyl ketone in a proportion resulting in a final viscosity about 1500 centipoises.
A 90~ basis weight decorative alpha cellulose sheet is coated on its decorative face side with a reverse direction roll coater containing the above-described resin. The film applied is then dried in an oven having graduated temperature zones as described in Example 1. The exiting shee~ has a resin content between 30% and 60% with volatiles held to less th~n 5%.
Predetermined lengths of the partially saturated decorative sheet are layed-up and consolidated with the polyester coated and U.V. "B" staged release sheet (as set forth in ~xample 1) as folLows:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg decorative sheet, 37% resin content Melamine-formaldehyde treated barrier sheet 55% resin content '~3 ll-Phenolic treated kraft paper sheets 35-40~ resin content 122# basis wt.

-The procedure of Example 17 was followed with a lay-up as ~ollows:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg decorative sheet 42% resin Melamine-formaldehyde overlay 50~ resin 7-Phenolic treated kraft paper sheets 34-38% resin Melamine-formaldehyde overlay - 65% resin EXAM~LE 19 The procedure of Example 17 was followed with a lay-up as follows:
Polyester coated and U.V. "B" staged release sheet Polyester Pre-Preg decorative sheet 46% resin Melamine-formaldehyde overlay 48% resin 9-Phenolic treated kraft paper sheets 35% resin Dry crepe Dry o~erlay An isophthalic polyester resin solution having a viscosity between 1000 and 2000 centipoise is prepared consisting of Ashland Chemical Company's 7220 resin, 1% triganol 14 (Noury Chemical Company), 0~75% t-butyl perbenzoate, 800 PPM (.08%
pluronic surfactant (BASF Wyandotte Corporation) and 500 PPM
(.05%3 BHT inhibitor.
A 65 lb. basis weight decorative alpha cellulose sheet is coated on its face surface with the above-described resin solution to a thickness of about 15-20 mils. "B" stage curing is ~ccamplished with the U.V. processor described in Example 1.
Predetermined lengths o~ the coated decorative sheet are layed-up in the following order and consolidated as described in ~16-Example 1:
Polyester decorative sheet that has been coated with 15-20 mils of U.V. "B" staged polyester resin.
Melamine-formaldehyde treated overlay - 55% resin content S-Phenolic treated kraft paper, 42% resin 132# basis wt.
Dry crepe Dry overlay Example 20 is repeated with the following lay-up:
Polyester decorative sheet that has been coated as in Example 20 Melamine-formaldehyde overlay - 50% resin ll-Phenolic treated kraft paper - 40% resin 122# basis wt.

Example 20 is repeated with the following lay-up:
Polyester decorative sheet that has been coated as in Example 20 Melamine-formaldehyde barrier sheet 48% resin 3-Phenolic treated kraft paper - 44% resin 132~ basis wt.
Melamine-formaldehyde overlay - 70% resin Laminates prepared as described in the examples above had physical properties above NEMA standard values and displayed stain and chemical resistance in excess of conventional melamine-formaldehyde high pressure laminates.

Claims

WHAT IS CLAIMED IS:
1. A process for producing a decorative laminate comprising:
A. applying a polyester resin to a decorative sheet;
1. curing said resin;
B. preparing an assembly of superimposed sheets by

1. placing said decorative sheet upon a dry sheet;
2. placing beneath said dry sheet a plurality of thermosetting resin impregnated sheets; and, C. consolidating said assembly under heat and pressure to a unitary laminated structure.

2. The process of Claim 1 wherein said polyester resin impregnates substantially the entire decorative sheet.

3. The process of Claim 1 wherein a melamine-formaldehyde resin impregnated sheet is positioned directly beneath said dry sheet.

4. The process of Claim 1 wherein said polyester resin is cured to a semi-solid state by radiation.

5. The process of Claim 2 wherein the polyester resin content of said decorative sheet in step B.1 is about 60-90% of the total weight.

6 . The process of Claim 5 wherein a melamine-formaldehyde resin impregnated sheet is positioned directly beneath said dry sheet.

7 . The process of Claim 5 wherein said polyester resin is cured to a semi-solid state by radiation.

8 . The process of Claim 5 wherein the viscosity of the resin in step A ranges between 700 and 3000 centipoise.