Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
  • D21J1/00—Fibreboard

Definitions

• This invention relates to a fibreboard having improved surface appearance and to a method for producing such fibreboard.
• this invention relates to pressed fibreboard which comprises both medium density building board and hardboard.
• Hardboard has previously been made having a printed paper overlay as described in US. Pat. 2,918,398 dated Dec. 22, 1959 for an invention of Rodger Malone Dorland, Maxwell Menuhin Yan and Elliott G. Heslop en titled Artificial Board.
• the method described in such patent has been used for producing wood grain and other effects.
• the realism which can be achieved with a printed paper overlay is limited and it is also difiicult entirely to eliminate uneven surface areas due to fibre clots in formation which produce an etfect referred to as hammer marks. Embossing so as exactly to match the printed pattern would be unduly costly. If the printing and the embossing are done at different stages in the process it would be difficult to obtain registration.
• wood chips are defibrated and refined in a conventional manner followed by forming and dewatering of the Wet lap on a Fourdrinier machine.
• a sheet of paper is applied to the wet lap when it has been dewatered to a consistency of about 25% to 40% solids content by weight.
• the sheet of paper is preprinted on its exterior surface with a pattern such as a wood grain representation.
• a drying oil such as linseed oil, soybean oil, tall oil, tung oil or a blend of drying oils with petroleum polymers is applied to the unprinted surface of the paper in the amount of about 1 to 5 lbs. of solids to 1000 sq. ft. of board.
• the drying oil not only enhance the bond between the paper and the base mat but it also imparts some translucency which increases the automatic shading obtained due to the embossing.
• the combined base mat and paper overlay is transferred to a hot press having its hot plates or caul plates which will be in contact with the paper surface shaped to provide an embossing of the surface with a complementary pattern to the printed pattern.
• a complementary pattern is one which has very approximately the same line spacing and configuration as the printed line pattern. No attempt is made to achieve registration of the printed pattern and the embossed pattern.
• the depth of draw which can be achieved without damaging the surface will depend on the contours of the pattern.
• a strip of wet uncoated paper pulled in a tester in the free state stretches 4.1% in length before breaking. Over a series of small embossed ridges about A" to /2" in length on a medium density board with a weathered pattern the stretch was -6%% with no visible tears. If A;" of length at a single valley was measured the stretch was 16% without visible failures. There may, however, have been microbreaks which were healed by the press, and there would also have been some displacement of the paper in relation to the base mat during pressing. It cannot therefore be expected that as much as 16% overall stretch could be achieved on an overall basis. It was, however, evident that the paper would stretch considerably more under restrained pressing conditions than would be possible in the free state. Embossing depths of 0.080 inch were achieved without paper breaks.
• the press cycle and, if desired, post press treatments such as baking can be those conventionally used for medium density board and hardboard.
• the combined base mat and paper overlay was then consolidated in a hot press at 350 F. using a striated pattern embossed aluminum caul plate depth of draw of approximately 0.020 inch as the top caul in contact with the printed overlay surface.
• a sheet of 25 lb. per ream (3000 sq. ft.) glassine paper was inserted between the embosing caul plate and the printed overlay prior to hot pressing.
• a conventional backing screen was used on the bottom surface of the board mat.
• the pressure cycle used was as follows:
• EXAMPLE 2 A fibrous wet lap was formed as in Example 1 except that the basis weight was 1350 lb. per 1000 sq. ft. (solids), and the wet lap was partially dewatered to 28% solids content by weight.
• Overlay was again applied to the top surface of the base mat but in this case the overlay was 32 lb. per ream (3000 sq. ft.) uncoated, printed newsprint sheet. Linseed oil was applied to the underside of the paper overlay as in Example 1.
• the combined base mat and paper overlay was consolidated in a hot press fitted with a deep, random weathered embossing top caul having a draw depth of up to 0.080 inch.
• Caul plate material was mild steel, chromed. No glassine intermediary sheet was used.
• a conventional backing screen was used on the bottom surface of the mat as. in Example 1. '1
• the hot press was fitted along the two side edges of the opening with slotted stopbars of 0.500 inch thickness. Press temperature was 400 F.
• the press was closed under 100 p.s.i. pressure (on board) and the overlayed wet mat compressed to stops in 30 seconds, at which point the pressure was immediately dropped to 40 p.s.i. (on board).
• the press was kept closed on the stops for minutes, then opened, the board removed and the backing screen separated from the board.
• the pressed, embossed board having an out-of-press moisture content of 15% was then heat treated in a conventional draught oven for 4 hours at 280 F. Finally a 1 /2 dry mil protective, clear finish was applied by conventional curtain coating.
• the resultant board had a thickness of 0.400 inch, a specific gravity of 0.68 and a highly attractive, deep embossed surface, shaded more darkly in the valleys than on the ridges, simulating weathered lumber.
• One of the advantages of the invention is that light weight, cheap, expendable caul plates can be used such as 4 light gauge embossed aluminum sheeting, plastics, photoengraving plates, textiles, papers and other textured webs and even natural objects such as leaves.
• a method of making pressed fibreboard having an improved surface appearance comprising preparing a partially dewatered wetv lap having a solids content of about 25 to 40% by weight of defibrated and refined wood chips, applying paper printed with a woodgrain line pattern to the partially dewatered wet lapwith the printed woodgrain pattern facing outwardly and then simultaneously embossing a non-registering pattern which is complementary in that it has very approximately the same line spacing and configuration as the printed woodgrain line pattern on the surface of the wet lap to which the printed paper has been applied and consolidating the printed paper and wet lap under heat and pressure in a press to provide a pressed fi-breboard.
• a 'method as in claim 1 in which a coating of drying oil is applied to the unprinted surface of the sheet of paper before the printed paper is applied to the partially dewatered wet lap.
• a method as in claim 1 in which a cushioning sheet is interposed between a hot plate or cual plate of the press and the printed paper before consolidatingunder heat and pressure.
• a pressed fibreboard comprising a base mat composed of fibers, a sheet of paper integrally combined with the base mat, a woodgrain line pattern printed on the exterior surface of such paper, and contours complementary to the printed woodgrain pattern in that they have very approximately the same line spacing and configuration but said contours not being in registration with the printed pattern embossed in the surface of such paper.
• a board as in claim 8 in which the contours are of such dimensions that the paper is stertched more than the maximum stretch of the paper in its free state but insufiicient to provide visible surface failure.
• a board as in claim 8 in which the contours embossed in the paper have valleys automatically darkened by the embossing to provide an auxiliary pattern and in which a layer of drying oil between the paper and the base mat gives translucency to develop such auxiliary pattern;

Landscapes

• Paper (AREA)
• Machines For Manufacturing Corrugated Board In Mechanical Paper-Making Processes (AREA)
• Laminated Bodies (AREA)
• Shaping Of Tube Ends By Bending Or Straightening (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=4142793

Family Applications (1)

Country Status (5)

Cited By (10)

Family Cites Families (2)

• 1967
  • 1967-11-17 US US683825A patent/US3576711A/en not_active Expired - Lifetime
• 1968
  • 1968-01-29 SE SE01131/68A patent/SE337984B/xx unknown
  • 1968-01-31 GB GB4914/68A patent/GB1168587A/en not_active Expired
  • 1968-02-01 NO NO00404/68*[A patent/NO129921B/no unknown
  • 1968-02-02 DE DE1653160A patent/DE1653160C2/de not_active Expired

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