PHENOL-BASED RESIN FOR THE PRODUCTION OF LAMINATES AND PROCESS FOR THE PREPARATION OF THE RESIN

Abstract: A Mg compound-containing phenol formaldehyde resin neutralized to a pH-range of 7,5 to 5 which resin alone or together with a melamine formaldehyde resin can be made cure rapidly and whereby, when using an impregnated paper in the body portion of a laminate, the laminate can be impressed with a dynamic or static compression, at a high or low pressure at an increased temperature and whereby the paper can be pressed to the surface of a building board over a short pressing time.

Description: Phenol-based resin for the production of laminates and process for the preparation of the resin The present invention relates to the preparation of a phenol-based resin and to its application for the pro¬ duction of laminates over a short pressing time as well as to a paper impregnated therewith and to its applic¬ ation for coating building boards over short pressing times or at low temperatures. Short pressing times have become necessary as a result of the introduction and development of continuous- action laminate presses. Likewise, short pressing times can be applied when pressing film coatings e.g. with a so-called rapid-cycle process or when using pressing temperatures even lower than earlier for the types of boards or structures that do not tolerate high pressing temperatures. Traditionally, so-called high-pressure laminates have been manufactured from phenolic resin impregnated base papers and melamine resin impregnated decor or facing papers by compressing over a long pressing time (circa 30 min) at high pressures (7 to 10 MPa) at a temperature of 120 to 160 * C by means of multi-die presses. As for continuous-action lamination, the traditional phenolic resins used for a laminate body section are too slow. In continuous-action lamination, papers im¬ pregnated with melamine-based resins have been used for the body section. These have achieved a sufficient curing rate but a drawback is the high price and the requirement of traditional high-pressure laminate stan¬ dards about the use of a phenolic resin in the body section. A few Patent applications have been published about fast phenol-based resins that are. suitable for con¬ tinuous-action pressing and useable for the impregnat¬ ion of a body section, wherein the mixture of a tra¬ ditional phenolic resin and a traditional melamine resin is cured in the presence of acid-delivering curing agents or in a corresponding system there is additional-: ly used a cross-linking acrylic resin or the curing of a phenolic resin has been accelerated by the addition of a resorcinol-based resin or some of the phenol has been replaced with alkyl phenol. A drawback of such processes is often an insufficient curing rate and/or a price much higher than that of traditional phenolic resins. It has been necessary to develop a fast-curing phenol formaldehyde "resin, .whereby an impregnated film can be hot-pressed to the surface of a bulding board (ply¬ wood, particle board or the like) in 3 to 4 minutes in otherwise similar conditions or which can be pressed at 110 to 120°C in otherwise similar conditions or which can be pressed at IT ' O'C within 40 to 60 seconds. The main object of this invention is tp provide a fast- curing phenolic resin, which is suitable for the con¬ tinuous-action production of laminates, useable in the body section and which is highly suitable for pressing together with a melamine coating film. A phenolic resin fulfilling this requirement has been obtained by catalyzing a phenolic resin as early as in its preparation, stage with suitable magnesium compounds or by adding g-salts into a traditionally formulated phenolic impregnation resin. The amount of magnesium compound can be varied as ex¬ pressed in moles of phenol from 0.01 to 0,3. The most preferred molar ratios have been found to be from 0,05 to 0, . The formaline and phenol molar ratio of such resin may vary from 1,2 to 3,0. However, 1,7 to 2,0 has been found optimal. A special feature found in magnesium-catalyzed phenolic resins is that their curing rate increaes significantly when proceeding from the traditional low cure pH-ranges (pH appr. 8 to 11) to the neutral pH-range (pH circa 7). In contrast, the traditional NaOH-, K0H-, K-CO.,-. Na^CO,-, Ba(OH) 2 - etc. catalyzed phenolic resins decrease their curing rate when approaching the neutral pH-range. The curing rate of these resins only begins to increse sig¬ nificantly in the strongly acidic pH-range (pH circa 3 or below). The neutral or slightly acidic pH-range in terms of the rapid curing of a phenolic resin is preferable in the sense that a melamine resin, possibly admixed in the impregnation of the body section, advantageously cures within the same pH-range. Also a melamine-formaldehyde resin used for the impregnation of a coating or decor film cures optimally in the same pH-conditions. When producing a laminate by using in the body section a phenolic resin curing within an alkaline range and in the surface layer a melamine resin curing within an acidic range, there will easily occur problems in the boundary surface between the layers; delamination, bubbling, incomplete curing etc. When impregnating the body section by using a mixture of traditional phenol formaldehyde and melamine formal¬ dehyde resins and by curing it in an alkaline, neutral or slightly acidic pH-range, there easily occurs in¬ complete curing of either one of the resin components over short pressing times, nor does the obtained lami¬ nate fulfil the requirements in all respects. The manner of increasing the curing rate of phenolic resin according to the invention is also preferable in the respect that magnesium ions have been found to in¬ crease also the curing rate of melamine resin and is therefore advantageous when used together with melamine formaldehyde resin in admixed form or with a melamine resin impregnated coating film in laminated form. A phenolic resin and a mixture of phenol melamine resins of the invention have been found to have a gelling rate ' .of 25 to 40 at 150°C depending on receptivity and pH, the base papers impregnated with a similar resin or resin system being pressable into a laminate by using a continuous-action press at an operating speed of 10 to 15 m/min, a temperature of 160 to 180°C, and a press¬ ure of 2 to 5 MPa. Another object of this invention is to provide a rapid- curing phenol formaldehyde resin suitable for the im¬ pregnation of paper for hot-pressing an impregnated film to the surface of a building board at a sufficient speed by using so-called rapid-cycle pressing. A phenolic resin fulfilling the requirements has been produced by the above-described processes from a phenolic resin suitable for continuous-action lamination. A paper impregnated with the phenolic resin or the mix¬ ture of phenolic and melamine resins of the invention can be hot-pressed to the surface of a building board at a temperature of 130'C, at a pressure of 2 MPa in 3 to 4 minutes and at a temperature of 120 β C, at a pressure of 2 MPa in 6 to 7 minutes and in so-called rapid-cycle pressing at a temperature of 170 * C and a pressure of 2 MPa in 40 to 60 seconds. The invention will be illustrated in more detail in the following examples. It should be appreciated that the details set forth in the examples are not to be considered to limit this invention. Examples Example 1 This example describes a resin curing rate in differ¬ ent pH-conditions. * A phenol ' formaldehyde resin was prepared with a molar ratio phenol : formaldehyde : Mg 2+ = 1 ,8 : 1 : 0,104. metered into a reactor: phenol 1 226 kg formaline 40 % 1 620 kg water 101 kg •Mg(OH) 2 73 kg The mixture temperature was raised to 85°C and was held there until viscosity had risen, as measured with a 4 mm Din cup at 20 * C, to 18 seconds. Thereafter, the condensation was stopped by cooling the resin to 20 to 25 * C. Properties of the resin are described by the following analysis values: pH 8,50 viscosity Brookfield 20° MPa s 49 specific weight 20° 1,147 dry matter content 1 g/1,5 h/150°C % 47,3 water tolerance 20° g/g 0,37 curing time 150°C s 74 The resin pH was adjusted with a 25 % hydrochloric acid and curing rate was measured. The results are set forth in the following table: pH Curing time 150°C, s 8,5 74 8,0 57 7,5 29 6,5 28 6,0 26 Example 2 A phenol formaldehyde resin was prepared with a molar ratio formaldehyde : phenol : Mg + = 1,8 : V : 0,05 by metering into a reactor: phenol 92 % 1 226 kg formaline 40 % 1 620 kg water 101 kg Mg(0H) 2 35 kg The mixture temperature was raised to 85°C and was held there until viscosity had risen, as measured with a 4 mm Din cup at 20°C, to 18 seconds. Thereafter, the mixture was cooled to 20 to 25°C and 144 g of methanol was added therein. Some of the mixture was neutralized with a 25 % hydro¬ chloric acid to pH 7,0. The analysis results of unneutralized and neutralized resin are set forth in the following table: Unneutralized Neutralized pH 8,20 7,50 Viscosity 80 48 Brookfield 20 * MPa s Specific weight 1,143 1,145 Dry matter 47,3 47,9 1 g/1,5 h/150 * C Water tolerance 0,23 0,03 Curing time 81 39 Example 3 A phenol formaldehyde resin was prepared at a molar ratio formaldehyde : phenol : mg-base = 1,8 : 1 : 0,05 by metering into a reactor: phenol 405 kg formaline 535 kg agnesiumoxide 8 kg The mixture was heated to the temperature of 85°C for 2 hours to achieve a suitable viscosity level and cool¬ ed to 20°C. Some of the water was replaced, a solvent, in this case methanol, was added and metered 50 kg. Prior to impregnating the laminate base paper, the resin pH was adjusted to pH 7,0 with a 50 % paratoluene sulphonic acid. Properties of the resin are set forth in the following table: pH 7,1 Viscosity 35 MPa s Specific weight 20° 1,141 Dry matter content 47,2 1 g/1,5 h/150'C Water tolerance g/g 0,59 Curing time 150°C s 52 Depending on a desired type of laminate there were still added necessary post-forming additives and/or release agents. The resin was used to impregnate a Kraft paper having 2 160 g/m to the amount of resin of 35 % in a convention¬ al manner and the thus impregnated paper was used to produce laminate in a continuous action together with a coating film impregnated with a suitable melamine resin. In the production of laminate, temperature was 160'C, pressure load was 3,5 MPa, and production line rate was 6 m/min. The laminate fulfilled the general quality requirements of post-forming high-pressure laminates. Example 4 A resin according to example 3 was prepared and per 90 parts by weight was mixed 10 parts by weight of a post-forming quality melamine formaldehyde resin having the same dry matter (melamine resin was Melurex 5002 from Priha Oy) . The resin mixture had a pH of 7,2 and its curing rate was 40 s/150°C. The resin mixture was used to impregnate a Kraft paper 2 having 160 g/m to the amount of resin of 35 % in a conventional manner and the thus impregnated paper was used to produce laminate in a continuous action togeth¬ er with a coating film impregnated with a suitable mel¬ amine resin. The laminate production conditions were: temperature 160°C, pressure load 3,5 MPa and rate 10 / min. The laminate fulfilled the general quality re¬ quirements ofpost-forming high-pressure laminates. Example 5 A resin according to example 3 was prepared and per 85 parts by weight was mixed 15 parts by weight of a post- forming quality melamine formaldehyde resin having the same dry matter (melamine resin was Melurex 5002 from Priha Oy) . The resin mixture had a pH of 7,3 and its curing rate was 32 s/150°C. The resin mixture was used to impregnate a Kraft paper 2 having 160 g/m to the amount of resin of 40 % in a conventional manner and the thus impregnated paper was used to produce laminate in a continuous action togeth¬ er with a coating film impregnated with a suitable mel¬ amine resin. The laminate production conditions were: temperature 160°C, pressure load 3,5 MPa and rate 12 m/ min. The laminate fulfilled the general quality re¬ quirements of post-forming high-pressure laminates. Example 6 A phenol formaldehyde resin according to example 3 was prepared. Prior to impregnation, colourants and a release agent were added into the resin as necessary. The resin was used to impregnate a Kraft paper having 2 42 g/m in a manner that the total weight was 117 g/m and residual moisture content was 6 to 8 %. The film was then pressed in a hot press to the surface of a plywood board at the temperature of 130°C and the pressure of 1,8 MPa in 4 minutes, whereafter the board fulfilled the normal standards.

Claims: Claims 1. A rapid-curing thermosetting plastic resin which is an Mg compound-containing phenol formaldehyde resin or a mixture of the above and an amino formaldehyde resin, c h a r a c t e r i z e d in that following a condensation occurring in an alkaline pH-range, the resin is neutralized with an acid or an acid-delivering compound to a pH-range of 7,5 to 5. 2. A phenol formaldehyde resin as set forth in claim 1 or a mixture thereof and an amino formaldehyde resin, c h a r a c t e r i z e d in that in the phenol formal¬ dehyde resin, the molar ratio of Mg to phenol is 0,01 to 0,3, preferably 0,05 to 0,1. 3. A process for the preparation of the resin set forth in claims 1 and 2, c h a r a c t e r i z e d in that an Mg-base is used as a catalyst for the phenol formaldehyde resin. 4. A process for the preparation of the resin set forth in claims 1 and 2, c h a r a c t e r i z e d in that the catalyst used for resin production is a magnesium base or an Mg-ions delivering compound along with some other generally known phenolic resin production catalyst. 5. A process for the preparation of the resin set forth in claims 1 and 2 by employing some generally known catalyst as a catalyst for the preparation of phenolic resin, c h a r a c t e r i z e d in that an Mg-compound is added in the resin either before or after a pH-adjust- ent effected within a pH-range of 7,5 to 5. 6. A process for the preparation of the resin set forth in claims 1 and 2, c h a r a c t e r i z e d in that the resin has a molar ratio formaldehyde : phenol of 1,1 to 3,0. 7. A method for the production of thermosetting plastic laminates by a per se known flat or continous-action technique from one or more impregnated films, c h a r - a c t e r i z e d in that the films are impregnated with a resin as set forth in claims 1 to 6. 8. A method for the production of thermosetting plastic laminates from one or more amino formaldehyde resin im¬ pregnated coating films and from one or more basic sheets, c h a r a c t e r i z e d in that the basic sheets are impregnated with a resin as set forth in claims 1 to 6. 9. A method for the production of a laminated board article by coating in a per se known manner a wood- or mineral-based board with a film, c h a r a c t e r ¬ i z e d in that the film is impregnated with a resin as set forth in claims 1 to 6.

Inventors: HIETANEN EERO, PIRHONEN ILPO, HIETANEN, EERO, PIRHONEN, ILPO
Applicants: PRIHA OY
Application year: 1987
Main classification: B32B27
IPC codes: B32B27, C08G8, C08L61, D21H17