Relatively inexpensive thermoformable mat and rigid laminate formed therefrom

A cellulosic fiber reinforced thermoformed laminate having a density of approximately 60 to 75 lbs./ft..sup.3 formed by the application of heat and pressure to a plurality of the mats while in a stacked configuration having a single ply thickness of approximately 15 to 60 mils and a density of approximately 25 to 45 lbs./ft..sup.3 capable of undergoing densification and thermoforming consisting essentially of a substantially random array of:

• (a) approximately 15 to 50 percent by weight on a dry basis of natural relatively coarse cellulosic fibers having a Canadian standard freeness at 0.3 percent consistency greater than 600 ml.,
• (b) approximately 10 to 25 percent by weight on a dry basis of thermoplastic synthetic polymer fibrils having a melting temperature below 450.degree. F.,
• (c) approximately 15 to 30 percent by weight on a dry basis of substantially non-fibrous solid particulate thermoplastic synthetic polymer particles having a particle size of approximately 0.075 to 0.6 mm. and a melting temperature below 450.degree. F., and
• (d) approximately 35 to 60 percent by weight on a dry basis of substantially void-free substantially water-insoluble particulate inorganic material,
• with said mats being substantially free of a binder and said components (c) and (d) being substantially dispersed among and substantially physically retained via entrapment by said components (a) and (b), wherein the temperature during the application of said heat and pressure was in excess of the melting temperature of said thermoplastic synthetic polymer of said components (b) and (c) and densification and thermal bonding took place within and between adjacent mats.

A process for forming a mat having a single ply thickness of approximately 15 to 60 mils and a density of approximately 25 to 45 lbs./ft.sup.3 capable of undergoing densification and thermoforming upon the application of heat and pressure which consists essentially of a substantially random array of:

• (a) approximately 15 to 50 percent by weight on a dry basis of natural relatively coarse cellulosic fibers having a Canadian standard freeness at 0.3 percent consistency greater than 600 ml.,
• (b) approximately 10 to 25 percent by weight on a dry basis of thermoplastic synthetic polymer fibrils having a melting temperature below 450.degree. F.,
• (c) approximately 15 to 30 percent by weight on a dry basis of substantially non-fibrous solid particulate thermoplastic synthetic polymer particles having a particle size of approximately 0.075 to 0.6 mm. and a melting temperature below 450.degree. F., and
• (d) approximately 35 to 60 percent by weight on a dry basis of substantially void-free substantially water-insoluble particulate inorganic material,
• with said web being substantially free of a binder and said components (c) and (d) being substantially dispersed among and substantially physically retained via entrapment by said components (a) and (b), wherein said process comprises the dewatering of an aqueous dispersion of components (a), (b), (c), and (d) by adding a flocculent to aid the agglomeration of particles, forming a wet web from said resulting aqueous dispersion through the use of a Fourdrinier machine from which excess water is drained, pressing the resulting web through the use of roller presses to remove additional water, and drying the resulting web through the use of a drier to further reduce the water content, while maintaining said mat at all times during its formation at a temperature below the melting temperature of components (b) and (c).