Heat and pressure consolidated laminate

A heat and pressure consolidated laminate made with a plurality of core sheets impregnated with an unsaturated polyester treating solution, the polyester providing the laminate with improved flexibility and enabling a core color that matches the color of the decor or face sheet.

The present invention relates to a heat and pressure consolidated 
decorative laminate having a plurality of core sheets impregnated with a 
polyester resin. 
BACKGROUND OF THE INVENTION 
Heat and pressure consolidated decorative laminates are generally produced 
utilizing a core material comprising a plurality of phenolic resin 
impregnated kraft paper sheets, a face sheet impregnated with a 
melamine-formaldehyde resin and optionally a melamine resin impregnated 
overlay sheet. These high pressure laminates, examples of which are 
described in the Grosheim et al U.S. Pat. No. 3,418,189, the Casey et al 
U.S. Pat. No. 4,311,748, and the Jaisle et al U.S. Pat. No. 4,473,613, 
have found world-wide acceptance as construction materials, i.e., wall 
panels, countertops, etc. in the home and office. They can be prepared so 
as to function in a variety of service applications and can be produced 
with surfaces such as high gloss, a matte finish or an embossed finish. 
Recently, decorative laminates having melamine-formaldehyde impregnated 
core sheets have been proposed in order that the core has a color matching 
that of the face or decor sheet such that the dark edge line that is 
perceptible when conventional laminates are cut or worked is eliminated. 
However, it has been found that this achievement of color match of the 
core and decor sheet is achieved at the expense of flexibility. In this 
respect, U.S. Pat. No. 4,448,849 to Keeling et al shows the use of a 
melamine-formaldehyde resin containing a hydroxylmelamine for impregnating 
core sheets and/or the decor sheet and/or the overlay sheet to provide a 
laminate with a solid color edge matching that of the core surface, the 
laminate being post-formable but not as flexible as desired. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide a heat and pressure 
consolidated decorative laminate that has increased flexibility and a core 
color that matches the decor sheet. 
It is another object of the present invention to provide a more flexible 
high pressure decorative laminate comprising a thermosetting 
melamine/formaldehyde reaction product impregnated face sheet and a core 
made from a plurality of core sheets impregnated with an unsaturated 
polyester having an acid number no greater than about 90 for providing 
flexibility to the consolidated laminate as well as enabling the core to 
possess a close color match for the face sheet and/or the back sheet of 
the laminate. 
These and other objects will be apparent from the specification that 
follows and the appended claims. 
SUMMARY OF THE INVENTION 
The present invention provides a high pressure decorative laminate 
comprising (a) a thermosetting melamine/formaldehyde reaction product 
impregnated face sheet; (b) one or more core sheets impregnated with a 
composition comprising an unsaturated polyester having an acid number no 
greater than about 90 for providing flexibility to the laminate; and (c) 
an optional melamine/formaldehyde reaction product impregnated back sheet; 
the face sheet (a), the core sheets (b) and the optional back sheet (c) 
being consolidated by heat and pressure to provide a laminate having 
improved flexibility as well as being resistant to chipping, being easily 
fabricated and having a color in the core sheets that matches that of the 
face and back sheets. 
The present invention preferably provides a heat and pressure consolidated 
laminate comprising (a) a thermosetting melamine/formaldehyde reaction 
product impregnated face sheet; (b) two or more colored core sheets, each 
core sheet impregnated with a solution comprising an unsaturated polyester 
having an acid number no greater than about 90, and a catalyst for further 
polymerizing and thermosetting of the polyester, the impregnated core 
sheet treated to obtain about 20 to 70 weight percent resin and the 
impregnated core sheet dried to a volatile content of about 1 to 5 weight 
percent, and (c) an optional thermosetting melamine/formaldehyde reaction 
product impregnated back sheet; the resulting consolidated laminate having 
improved flexibility as evidenced by a wrap test conducted at ambient or 
room temperature in which the resulting laminate wraps around a 3 to 5 
inch radius compared to a current commercially available laminate with 
core sheets impregnated with a melamine/formaldehyde reaction product 
which wraps around a 5 to 6 inch radius. 
The present invention also provides, in another embodiment, a heat and 
pressure consolidated laminate comprising: (a) a polyester resin 
impregnated face sheet; (b) a plurality of core sheets impregnated with a 
composition comprising an unsaturated polyester having an acid number no 
greater than about 90 for providing flexibility to the consolidated 
laminate and a solvent for the polyester; and (c) an optional 
melamine/formaldehyde reaction product impregnated back sheet; the face 
sheet (a), the core sheets (b) and the optional back sheet (c) being 
consolidated by heat and pressure to provide a laminate having improved 
flexibility as well as being resistant to chipping, being easily 
fabricated and having a color in the core sheets that matches that of the 
face and back sheets. 
DETAILS OF THE INVENTION 
In general, in accordance with the invention, the core sheets are made by 
impregnating a cellulosic paper pigmented in color to conform with the 
color of the face sheet, and the face and back sheets produced by 
impregnating an alpha cellulose paper optionally containing a pigment or a 
print, pattern or design. Typically, a paper of about a 60 to about a 160 
pound basis weight per 3000 square foot ream is employed for the core 
sheets while the alpha cellulose sheet used in the face layer generally 
runs from about 40 to about 120 pound basis weight per 3000 square foot 
ream. The core sheets may be comprised of any of several saturating grade 
papers, such as alpha cellulose, bleached kraft or cotton linters paper, 
which are capable of being colored to a close match to the decor or face 
sheets. 
The unsaturated polyester for the core sheets that provides flexibility to 
the laminate generally is a reaction product of a polyhydric alcohol, a 
saturated dicarboxylic acid and an unsaturated dicarboxylic acid. The 
unsaturated polyester is preferably prepared from propylene glycol, 
isophthalic acid, and maleic anhydride. As is known the acid component 
generally is used in about 1.0 to 1.05 moles per mole of glycol. 
The unsaturated polyester for use in accordance with the invention does not 
affect the color of the pigmented core sheets as do the dark brown to 
black phenolic resins. It is also color stable over substantially longer 
periods of time than the phenolics. 
The unsaturated polyester can also be prepared by reacting propylene 
glycol, maleic anhydride and reclaimed polyethylene terephthalate (PET) 
resin from, for instance, carbonated beverage bottles. As is known, a 
catalyst is used for further polymerization of the polyester in preparing 
the core sheet impregnate, the catalyst being able to generate free 
radical polymerization initiators; i.e., organic peroxides, inorganic 
persulfates, the preferred catalyst being t-butyl perbenzoate. In the 
treating solution for impregnating the core sheets with the unsaturated 
polyester, a crosslinking monomer that is a vinyl, acrylic or allylic 
monomer can be used, such as styrene, methyl methacrylate, and 
diallylphthalate. 
The acid number of the unsaturated polyester is generally no greater than 
about 90, preferably about 10 or 15 to about 50 or 60 and more preferably 
about 18 or 20 to about 23 or 25. Excellent results have been obtained 
with an acid number of about 20, particularly for the polyester prepared 
from propylene glycol, isophthalic acid and maleic acid, such preferred 
polyester also having an SPI Gel test at 81.degree. C. of about 4.5 to 6.5 
minutes and a Brookfield Viscosity (25.degree. C.) of about 14 to 17 
poises (60/40 in styrene). 
In general, for the polyester the SPI Gel test runs about 2.5 or 3 minutes 
up to 7 or 8 minutes and the Brookfield Viscosity runs about 10 or 11 
poises up to 20 or 25 poises. 
In general, the reacting composition for impregnating each of the core 
layers contains about 30 to 60 parts by weight of the polyester, about 30 
to 60 parts by weight of acetone or other solvent for the polyester, about 
1 or 2 up to 8 or 10 percent by weight of t-butyl perbenzoate or another 
catalyst for further polymerization of the polyester and, optionally about 
1 to 70 percent by weight of a crosslinking monomer such as styrene. 
Preferably, the treating solution is about equal parts by weight of 
acetone and polyester, about 4 weight percent of t-butyl perbenzoate based 
on the weight of the polyester, and when used, about 5 to 15 percent by 
weight of the crosslinking monomer based on the weight of the polyester. 
The unsaturated polyester impregnated core sheets provides the resultant 
consolidated laminate with greatly improved flexibility, the laminate 
being flexible enough at ambient temperature to wrap around a 3 to 5 inch 
radius without breaking compared to a laminate with melamine/formaldehyde 
impregnated core sheets that can wrap only around a 5 to 6 inch radius. 
The polyester treating composition generally is a solution of about 20 to 
80 percent by weight solids, the preferred amount being about 40 to 60 
percent by weight, and the optimum amount being about 45 or 50 percent by 
weight. 
In impregnating the face sheet, as is known in the art, a thermosetting 
melamine/formaldehyde reaction product is used that is a precondensate 
prepared from generally about 1.0 to 2.7 moles and preferably about 1.75 
to 2.25 moles of formaldehyde per mole of melamine. Optionally, small 
amounts, e.g., about 1 to 20 weight percent based on the weight of the 
reaction product, of modifiers can be used, such modifiers including 
dicyandiamide, ortho-para-toluenesulfonamide, sucrose, and glycols such as 
diethylene glycol. 
As previously indicated, the face sheet can be impregnated by a polyester 
resin, preferably the same unsaturated polyester resin used in 
impregnating the core sheets. 
In some cases although not preferred, a resin system for impregnating the 
face sheet or even the core sheets can be used that is a blend of melamine 
(about 15 to 25 weight percent) and a polyester resin (about 75 to 85 
weight percent) as described in the Richardson U.S. Pat. No. 2,809,911. 
The Richardson patent does not describe a melamine/formaldehyde print face 
sheet and there are dissimilarities between the Richardson patent 
structure and the laminate in accordance with the present invention 
including the nature and structure of the polyester molecule used, the 
resin content of the core, the treating methods and drying time, the 
laminating pressures and the laminate construction. 
In preparing the multiple resin system decorative laminates of the 
invention, excellent results have been obtained with about 5 to 9 and 
preferably 6 or 7 core sheets impregnated with the unsaturated polyester 
treating solution at a resin content of about 38 to 42 weight percent, and 
dried at about 180.degree. to 220.degree. F. to a volatile content of 
generally about 1.5 to 4 percent by weight and preferably about 2 or 3.5 
percent by weight. 
The resulting laminates are generally about 0.05 to 0.07 inches in 
thickness, have improved flexibility as well as good color match, and 
possess the desirable properties of resistance to chipping, punchability, 
ease of handling and fabrication as well as retaining the normal 
expectations on stain resistance, scratch resistance, surface wear, etc. 
A preferred process for manufacturing a laminate of the present invention 
comprises stacking the impregnated sheets, after at least partial drying, 
in the desired number and configuration and placing the stack between 
stainless steel press plates. An optional texturizing sheet may be used 
and placed between the face sheet and one of the plates to provide gloss 
and texture to the face sheet, the texturizing sheet being removed after 
pressing. Thereafter, a pressure of from about 800 to 1400 psi at 
temperatures from about 240.degree. F. to 350.degree. F. is exerted on the 
press plates for periods of from 20 minutes to 90 minutes to effect the 
cure and thereby provide the high pressure decorative laminate.

The following example is intended to illustrate the invention but not to 
limit it in any way. 
EXAMPLE 
A print or face sheet was prepared by treating a roll of pigmented 
alpha-cellulose decorative paper with a melamine/formaldehyde reaction 
product, the paper being one with a basis weight of approximately 69 
pounds per 3000 FT.sup.2. The melamine/formaldehyde reaction product was 
prepared by reacting 2.0 moles of formaldehyde per mole of melamine and 
adding 2 percent by weight of dicyandiamide as a modifier. 
The web of paper was carried through a resin filled dip pan, over sky rolls 
for better penetration, and through squeeze rolls to obtain a resin 
content of 55 percent. The web was dried in a treater oven to a volatile 
content of 5 percent and the proper sheet lengths were cut from the web. 
The unsaturated polyester impregnated core sheet was prepared by treating a 
roll of pigmented alpha-cellulose decorative paper with a basis weight of 
97 pounds per 3000 FT.sup.2 in a polyester resin. The resin was prepared 
by reacting propylene glycol, isophthalic acid and maleic acid to provide 
a polyester having an acid number of 20. The polyester resin was diluted 
to a 50 percent solids solution using acetone as the solvent and 4 percent 
tertiary butyl perbenzoate was added to catalyze the polyester. The 
unsaturated polyester resin solution was as follows: 
Polyester Resin Solution 
100 pounds Polyester 
100 pounds Acetone 
4 pounds Tertiary Butyl Perbenzoate 
The web of alpha-cellulose paper was carried through the polyester resin 
filled dip pan and through mayer rods to obtain the desired resin content 
of 40 percent. The web was dried to a volatile content of 2 percent and 
cut to a sheet length comparable to the print sheet. 
The solid color laminate was constructed as by assembling the component 
sheets as illustrated below. 
1 Texturizing Paper (clay filled alpha-cellulose paper) 
1 Melamine Treated Print Sheet (Face Sheet) 
6 Polyester Treated Core Sheets 
1 Melamine Treated Print Sheet (Back Sheet) 
The sheets were consolidated in a hydraulic press under 1200 psi of 
pressure and at a temperature of 285.degree. F. for a total cure cycle of 
one (1) hour. After pressing, the texturizing paper was removed and the 
laminate was trimmed and sanded. 
The resultant consolidated laminate met the required NEMA standards. The 
resultant laminate was resistant to chipping, easily fabricated and had a 
color in the core sheets that matches the face and back sheets. The 
laminate was flexible as evidenced by a room temperature wrap test in 
which the laminate wraps around a 3 to 5 inch radius.