Abstract A method of coating a contoured portion of a generally porous molded pulp article having sloping side and flat bottom wall portions with generally imperforate thermoplastic material to achieve a superior bonded product. First the article to be coated is placed against an open-face suction die, a flat continuous sheet of thermoplastic material is then placed in overlying relationship with the exposed portion of the die-supported article, the temperature of the thermoplastic material is raised to the range where it is sufficiently ductile to closely conform with the contoured portion of the molded pulp article, the thermoplastic material is suction adhered into intimate physical contact with the article without undesireable pleats or folds, a closed chamber is created around the article and its adhered thermoplastic material with the open-face suction die forming a portion thereof, the pressure within the closed chamber is increased to act against the exposed portion of the thermoplastic material with a pressure at least twice atmospheric pressure, and finally the temperature of the thermoplastic material continues to be raised until a mechanical bond with the contacted pulp is effected which is characterized in the finished product by a substantially uniform penetration of thermoplastic material into the adjacent pulp material on the sloping side as well as the flat bottom wall portions and the penetration of fibrous pulp material into the adjacent side of the thermoplastic material is also substantially uniform as to both quantity and depth of penetration on the side as well as the bottom wall portions so that a substantially equal amount of force is required to forceably separate the thermoplastic as a sheet from a given area of the bottom wall portions and from a given area of the side wall portions, and so that a substantially uniform amount of pulp material per area unit adheres to the thermoplastic material from the side as well as the bottom wall portions at any place over the bonded surface of the thermoplastic material when it is forceably separated as a sheet from the remainder of the product.
A method of coating a contoured portion of a generally porous molded pulp article with thermoplastic material which comprises placing the article to be coated against an open-face suction die, placing a flat continuous sheet of generally imperforate thermoplastic material in overlying relationship with the exposed portion of the die-supported article, raising the temperature of the thermoplastic material to the range where it is sufficiently ductile to closely conform with the contoured portion of the molded pulp article, suction adhering the thermoplastic material into intimate physical contact with the article without pleats or folds, creating a closed chamber around the article and its adhered thermoplastic material with the open-face suction die forming a portion thereof, increasing the pressure within the chamber to act against the exposed portion of the thermoplastic material with a pressure at least twice atmospheric pressure, and continuing to raise the temperature of the thermoplastic material until it effects a mechanical bond with the contacted pulp.
Claim 2
Dependent Claim
35 words
A method of coating a molded pulp article with thermoplastic material as in claim 2 wherein the temperature of the molded pulp article itself is raised until the thermoplastic material effects a mechanical bond therewith.
Claim 3
Dependent Claim
131 words
A method of coating a contoured portion of a generally porous molded pulp article with thermoplastic material as in claim 2 wherein the flat continuous sheet of generally imperforate thermoplastic material is from about 0.5 to about 1.0 mil in thickness, the porous molded pulp article comprises an after-pressed sheet approximately one thirty-second of an inch thick, the sheet of molded pulp material and the sheet of thermoplastic material are first heated for a Time not exceeding about 20 seconds, and the temperature is thereafter raised to a bonding range from about 250* F. to about 450* F. for a time not exceeding about 18.0 seconds with the fluid pressure applied in the range of about 100 p.s.i. and the suction being in the range of about 25 inches of mercury.
Claim 4
Independent Claim
139 words
A method of coating a dish shaped generally porous molded pulp article having a laterally outwardly flanged marginal rim portion therearound with thermoplastic material which comprises placing a continuous sheet of generally imperforate thermoplastic material in overlying relationship with one side of the article, raising the temperature of the thermoplastic material to the range where it is sufficiently ductile to closely conform with the molded pulp article, suction adhering the thermoplastic material into intimate physical contact with the one side of the article and with the outer peripheral edge of the rim portion as well as with the other side of the rim portion in doubled-back underlying relationship, and continuing to raise the temperature of the thermoplastic material to the bonding point while applying pressure to effect a mechanical interlocking of pulp material and thermoplastic material at their interface.