GB1573711A

GB1573711A - Decorative sheet of laminated material and preliminary chipboard product capable of high-grade finish

Info

Publication number: GB1573711A
Application number: GB47282/76A
Authority: GB
Original assignee: ROEMMLER H RESOPAL WERK GmbH; Resopal Werk H Roemmler GmbH
Current assignee: ROEMMLER H RESOPAL WERK GmbH; Resopal GmbH
Priority date: 1975-11-12
Filing date: 1976-11-12
Publication date: 1980-08-28
Also published as: FR2331440A1; CH624341A5; LU76175A1; SE7612505L; IT1073837B; NL7612413A

Abstract

A chipboard is impregnated with a resin solution such that a resin content in the chipboard of 8 to 45% is produced. In a subsequent drying process, the volatile components are reduced to 5 to 12% by weight based on the entire weight of the chipboard, the complete curing of the introduced resin proportion being prevented, so that the resin or portions thereof still have flowability at least at pressures of 120 kp/cm<2> and a temperature of 150 DEG C. The chipboard thus treated is pressed directly after drying or at a subsequent time with a decorative layer at a pressure of 50 to 120 kp/cm<2> and a temperature of 120 to 180 DEG C. Commercial chipboards can be used.

Description

(54) DECORATIVE SHEET OF LAMINATED MATERIAL AND PRELIMINARY CHIPBOARD PRODUCT CAPABLE OF HIGH-GRADE FINISH (71) We, RESOPAL WERK H. Röm- mler GmbH, of 6800 Mannheim-Kaefertal, Kallstadter Strasse 1, Germany, a Germanay Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to chipboard products based on vegetable material, in particular wood chips, and to decorative sheets of laminated material incorporating chipboard.

Many known chipboards have a content of thermosetting resins below 8%. These plates have poor water resistance and poor mechanical properties, having specific weights of below 0.75 g/cm3 because of cavities in the board. Consequently, coated sheets can be pressed in by the application of a slight force on the surface. Chipboards with a higher content of thermo-setting resins are also known. But even a somewhat higher resin content does not impart a considerable improvement in rigidity and water resistance.

Thin chipboards, down to thickness of approximately 2.2 mm. can be produced by a special production method, this being impossible with the conventional methods (see German Patent Specification 2 094 867).

But chip plates produced by even this method do not differ fundamentally, as to their properties from those referred to above. Recently thin chip boards have been produced by yet another method [see the journal "Holz als Roh-und Werkstoff" 33 (1975), pages 370 to 375]. Because of their high density, up to 1.1 g/cm3, these chipboards have improved water resistance and higher rigidity.

However, all the boards referred to above have the disadvantage that they do not permit subsequent deforming processes and/ or high-grade finish methods which take place at pressures above approximately 30 kp/cm2. At higher pressures destruction of the internal structure of the board must be expected.

In view of the fact that a considerable portion of the chipboard production is to be subjected in a subsequent process to an improvement which leads to high-grade products which are highly water resistant and can be mechanically highly loaded, the development of a chipboard (preliminary chipboard product) which is not yet hardened and which, because of its properties, permits variation in the processes of the further manipulation was recognised as a desirable object.

The present invention in one aspect resides in a method of producing a chipboard comprising vegetable material bonded with a thermosetting resin in an amount of 8 to 45% by weight, wherein the vegetable material and resin are formed into a board and the board is subjected to a resinhardening treatment which is arrested before the resin is fully hardened, whereby the chipboard thus produced contains thermosetting resin which is still flowable under the effect of pressure and heat.

The chipboard consists preferably of wood chips. Alternatively it may be made from different vegetable material, such as fibres of annual plants. A resin content of from 15 to 35% by weight is preferred.

All suitable thermo-setting resins may be used for the production of the chip board.

Urea, phenol and melamine resins and mixtures thereof are preferred.

The chipboard can be produced in the usual manner on conventional machines, however, the temperature adjustment and the travel speed must be so controlled that complete hardening of the resin does not occur, i.e. so that the resin is still flowable under pressure and increased temperature.

The resin is preferably flowable at least at pressures of 120 kg/cm2 and at a temperature of 1500C.

The invention in another aspect resides in a method of producing a chipboard comprising vegetable material bonded with a thermosetting resin in an amount of 8 to 45% by weight, wherein a chipboard bonded with a fully hardened thermosetting resin is soaked with a thermosetting resin to obtain a total resin content of 8 to 45%, and the soaked chipboard is dried without hardening the resin incorporated by said soaking, whereby the chipboard thus produced contains thermosetting resin which is still flowable under the effect of pressure and heat. Thus, a substantially conventional chipboard, that is to say a hardened chipboard with a lower than usual resin content, e.g. 7 to 8% of fully hardened resin, is soaked in a resin solution or dispersion. In the subsequent drying process the volatile components are reduced preferably to 5 to 12% by weight referred to the total weight of the board.

Continuous production is possible by means of a combination of the usual method of producing fully hardened chipboard, with a subsequent soaking in resin and drying.

The present invention further resides in the manufactured product comprising a chipboard comprising vegetable material bonded with thermosetting resin in an amount of 8 to 45two by weight, the resin not being fully hardened and hence being still flowable under the effect of heat and pressures above 30 Kp/cm2 without destruction of the internal structure of the board.

In conventional chipboard-making procedures the material being processed will necessarily pass through an intermediate stage where it will be in the form of a board in which the resin is not competely hardened. however in the present invention the "manufactured product" is obtained as a deformable and further curable product and thus is clearly distinguished from the intermediate-stage materials previously referred to.

A particular advantage of the chipboward according to the invention is that because of its incomplete hardening it possesses properties which permit optimum process conditions for further treatment, the complete hardening occurring only during a further treatment.

In contrast to normal chipboards, the board according to the invention can be utilized in finishing treatment processes which require a higher pressure than 30 kp/cm2, without destruction of the internal structure. The board permits further treatment at very high pressures. As the pressure increases, the density of the board increases and thus an improved water resistance and higher rigidity are obtained. It is thus possible, by the choice of the treatment conditions, to adjust desired properties of the finished product.

The board according to the invention may be subjected to further treatment by all methods which ensure subsequent hardening. Typical cases of application are all coating processes which are performed under pressure and heat.

The determination of the flowability of the resin or the proof of the incomplete hardening may be effected in accordance with the methods known in practice or described in the literature. A restriction to a definite test method is not required. The methods described below are to indicate possibilities: 1. Compression of the chipboard in a press under pressure and elevated temperature, and observation of the outflow of resin; 2. Production of a moulded part from the ground board under pressure and increased temperature; 3. Extraction of the resin from the board and determination of the flow properties in suitable test apparatus.

A further aspect of the invention is the production of a decorative sheet of laminated material with a core and a decorative layer on one or both sides, the core layer being or comprising a chipboard.

Production methods for sheets of laminated material of various kinds are already known. in which the sheet of laminated material comprises a decorative layer and a core layer. They are constructed from different web-like support materials, e.g. papers and fleeces, which are impregnated or coated with hardenable resins. In the production of a laminated material sheet a plurality of such webs of the same or different kinds are united under the effect of heat and pressure. Webs are caustic soda kraft paper as resin supports which are impregnated with phenol resin or cresol resin are used particularly frequently for forming the core layer. This is followed on one or both sides, to form a decorative layer, by at least one sheet of cellulose which is impregnated with urea resin or melamine resin and which can be in one colour ordecoratively printed. The total thickness of such laminated material sheets generally amounts to 0.7 to 1.5 mm.

In view of the economic expenditure necessary for converting wood or wood fibre products to paper, it appeared desirable to provide a method of producing laminated sheets with a core layer of wood fibre material or wood shavings material. Thereby the high costs for the production of the individual core papers as well as for the soaking thereof with resin can be dispensed with.

Accordingly the invention in a further aspect resides in a method of making a decorative laminate, wherein a chipboard according to the invention is pressed together with a decorative layer or layers at a pressure of from 50 to 120 kp/cm2 and at a temperature of of from 120 to 1800C.

The invention further resides in a method of producing a decorative sheet of laminated material with a core and a decorative layer on one or both sides, the core layer thereof being or containing a chipboard, in which method a chipboard having a content of thermo-setting resin of from 8 to 45% by weight which is not fully hardened and hence is still flowable under the effect of pressure and heat, is pressed together with the decorative layer or layers at a pressure of from 50 to 120 kp/cm2 and at a temperature of from 120 to 1800C.

The degree of hardening of the resin has been found to be particularly important and to differ from that of conventional clup- boards. It was necessary to start from chipboards which are not fully hardened. If conventional chipboards with fully hardened resins are used, overhardening of the previously hardened resin in the chipboard and destruction of the chipboard structure occur when the pressures of from 50 to 120 kp/cm2 and the temperatures of from 120 to 1800C necessary for producing the laminated sheet are applied.

The present method permits the production of decorative laminated sheets with the use of cores which do not consist of the multiple-layer expensive papers or fleeces.

It is also possible thereby to produce decorative laminated sheets economically in such thicknesses that they can be used without supports as self-supporting elements. The method permits the production of a product with higher water resistance and better rigidity than are possible with conventional methods.

The method of producing the decorative laminated sheet with the use of the chipboard of the invention will be explained in detail with reference to the following examples, in which percentages are given by weight.

Example I A commercial chipboard of 3 mm thickness having a phenol resin content of 7% was soaked in a 50% solution of a phenolresole resin so that a resin content of 20% was obtained. Subsequently the soaked plate was dried at llO"C in an oven to a residual content of 7% of volatile components, without hardening the additional resin incorporated in the board by the soaking.

A press parcel was formed with the following construction: Presser plate Decorative paper impregnated with melamine resin Caustic soda kraft paper impregnated with phenol resin Soaked and dried chipboard containing un-hardened resin Separating sheet Soaked and dried chipboard containing un-hardened resin Caustic soda kraft paper impregnated with phenol resin Decorative paper impregnated with melamine resin.

Twelve of these press parcels were placed between the heating plates of a multi-storey press and were heated to 1400C at 100 kg/cm2 and then cooled to 65"C in a cycle of 90 minutes to form decorative laminated sheets.

Example 2 A chipboard 2.2 mm thick and with a phenol resin content of 8% was soaked in a 48% solution of melamine resin so that a total resin content of 35% of which part was not hardened was obtained. The drying and the further treatment were effected as in Example 1. The pressing conditions were 60 kg/cm2, 160 C and 70 minutes.

Example 3 A commercial chipboard of 5 mm thickness with a urea resin content of 8% was soaked in a 48% solution of melamine resin so that a resin content of 12% of which part was not hardened was obtained. Drying was carried out according to Example 1 so that a residual content of volatile components of 5.5% remained.

For the production of the laminated sheets the following press parcel was formed: Presser plate Decorative paper impregnated with melamine resin Soaked and dried chipboard containing un-hardened resin Decorative paper impregnated with melamine resin Six of these parcels were pressed in a multi-story press for 90 minutes at 1300C and 120 kg/cm2 in accordance with Example 1.

Example 4 In apparatus for producing commercially available chipboard, a chipboard of 3 mm thickness and with a resin content of 18% phenol resin was produced in such a manner that the phenol resin was not fully hardened. It could be proved by extraction with alcohol that slightly more than half the resin was not hardened. Further treatment of the chipboard thus produced was effected as in Example 1.

Claims

WHAT WE CLAIM IS:

1. A method of producing a chipboard comprising vegetable material bonded with a thermosetting resin in an amount of 8 to 45% by weight, wherein the vegetable material and resin are formed into a board and the board is subjected to a resinhardening treatment which is arrested before the resin is fully hardened, whereby the chipboard thus produced contains thermosetting resin which is still flowable under the effect of pressure and heat.

2. A method of producing a chipboard comprising vegetable material bonded with a thermosetting resin in an amount of 8 to 45% by weight, wherein a chipboard bonded with a fully hardened thermosetting resin is soaked with a thermosetting resin to obtain a total resin content of 8 to 45%, and the soaked chipboard is dried without hardening the resin incorporated by said soaking, whereby the chipboard thus produced contains thermosetting resin which is still flowable under the effect of pressure and heat.

3. A method as claimed in claim 2 in which the drying is continued until the volatile components are reduced to 5 to 12% by weight of the total weight of the board.

4. A method according to claim 3 in which the board is produced, soaked and dried in a continuous manner.

5. A method of producing a chipboard, as claimed in claim 1 and substantially as described in the foregoing Example 4.

6. A method of producing a chipboard, as claimed in claim 2 and substantially as described in the foregoing Example 1, 2 or 3.

7. Chipboard comprising vegetable material bonded with thermosetting resin in an amount of 8 to 45% by weight, the resin not being fully hardened, when produced by the method claimed in any of claims 1 to 6.

8. The manufactured product comprising a chipboard comprising vegetable material bonded with thermosetting resin in an amount of 8 to 45% by weight, the resin not being fully hardened and hence being still flowable under the effect of heat and pressures above 30 kp/cm2 without destruction of the internal structure of the board.

9. A chipboard according to claim 7 or 8 in which the resin is such as to become flowable at least at pressures of 120 kg/cm2 and a temperature of 1500C.

10. A chipboard according to claim 7, 8 or 9 having a resin content of from 15 to 35% by weight.

11. A chipboard according to any one of claims 7 to 10 in which the thermosetting resin is a urea resin or a phenol resin.

12. A method of producing a decorative sheet of laminated material having a core and a decorative layer on one or both sides, wherein a chipboard as claimed in any of claims 7 to 11 and the decorative layer or layers are pressed together at a pressure of from 50 to 120 kp/cmand a temperature of from 120 to 1800C.

13. A method of producing a decorative sheet of laminated material with a core and a decorative layer on one or both sides, the core layer thereof being or containing a chipboard, in which method a chipboard having a content of thermosetting resin of from 8 to 45% by weight which is not fully hardened and hence is still flowable under the effect of pressure and heat, is pressed together with the decorative layer or layers at a pressure of from 50 to 120 kp/cm2 and at a temperature of from 120 to 1800C.

14. A decorative sheet of laminate material, made by the method claimed in claim 12 or 13.