Process for producing a formaldehyde-free furniture board

Abstract

The application provides a formaldehyde-free furniture plate production process, which comprises the following steps: S1. taking at least three veneers for cutting and drying treatment; S2. brushing adhesive on one side of two veneers located at the outermost sides, and completely immersing the remaining middle layer veneers in the adhesive; S3. pasting one middle layer veneer and one outer side veneer on one side of the veneer, performing first hot pressing treatment, and then cooling; S4. then sequentially pasting the remaining middle layer veneers with the previous middle layer veneer, and performing second hot pressing treatment after pasting each middle layer veneer, and then cooling; S5. then pasting another outer side veneer with the outer side of the pasted middle layer veneer, and performing third hot pressing treatment; the obtained plywood can be obtained after hot pressing and standing at room temperature; wherein the adhesive comprises modified sodium silicate 20-40 parts, boron nitride powder 5-10 parts and ammonium stearate 1-5 parts in terms of weight fraction; the obtained plate has strong bonding capacity, better mechanical strength and thermal stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of furniture board, in particular to a formaldehyde-free furniture board production process. BACKGROUND

[0002] The board can be divided into plywood, particle board, fiberboard and veneer according to the production raw material. It is mainly used for making furniture, building materials, packaging and transportation and living equipment.

[0003] The fiberboard is made of wood fiber or straw fiber and adhesive, and the adhesive mainly uses urea-formaldehyde resin, phenol-formaldehyde resin, etc. The board made of such adhesive will release harmful substances such as formaldehyde, has certain toxicity and peculiar smell and is easy to deform. The plywood is a three-layer or multi-layer board-shaped material made of wood segments rotary cut into veneers or thin wood cut from wood, usually with odd number of veneers, and the fiber direction of adjacent layers of veneers is perpendicular to each other. Due to its light weight, small heat transfer coefficient, good strength, easy processing and decorative veneer, it is widely used. The processing of plywood is simple, the energy consumption of production and processing is less, and the greenhouse gas emission is very low. Under the big situation of environmental protection, plywood has great advantages, so plywood has always played an important role in furniture board and is widely used.

[0004] However, the adhesives used in plywood are mainly urea-formaldehyde resin, phenol-formaldehyde resin, melamine-formaldehyde resin, etc. The most commonly used three aldehyde adhesives in the market release harmful substances such as free formaldehyde during production and use, which not only pollutes the air but also harms human health. Therefore, it is imperative to develop formaldehyde-free adhesives. Organic formaldehyde-free adhesives mainly include soybean protein, lignin, isocyanate, starch and thermoplastic resin adhesives. Inorganic adhesives have attracted widespread attention in recent years because they do not contain formaldehyde components. However, inorganic adhesives have the problems of high brittleness and poor mechanical strength, so it is necessary to improve them. SUMMARY

[0005] The present application relates to the technical field of furniture board, in particular to a formaldehyde-free furniture board production process.

[0006] The embodiment of the present application is realized by the following technical scheme:

[0007] A formaldehyde-free furniture board production process, comprising the following steps:

[0008] S1. Take at least three veneers, cut and dry them to have a water content of 5-9%;

[0009] S2. One side of the two outermost single boards is evenly brushed with adhesive, and the remaining middle layer single boards are fully immersed in the adhesive;

[0010] S3. One side of one middle layer single board is adhered to one outer single board, and the first hot pressing treatment is performed;

[0011] S4. Then, the remaining middle layer single boards are sequentially adhered to the previous middle layer single board, and the second hot pressing treatment is performed after each middle layer single board is adhered;

[0012] S5. Then, one side of another outer single board is adhered to the outer side of the adhered middle layer single board, and the third hot pressing treatment is performed; after hot pressing, the obtained plywood can be left at room temperature for 18-24 hours;

[0013] The adhesive comprises, by weight fraction, 20-40 parts of modified sodium silicate, 5-10 parts of boron nitride powder and 1-5 parts of ammonium stearate.

[0014] The technical scheme of the embodiment of the application has at least the following advantages and beneficial effects:

[0015] 1. The present application bonds each layer of board one by one, and performs hot pressing treatment and cooling one by one, so that the adjacent single boards can be bonded more stably, and the formaldehyde in the adhesive or the board and the bubbles that may exist in the adhesive can be removed; and as the number of single boards increases, the hot pressing temperature increases to meet the bonding strength between the single boards and to accelerate the movement of formaldehyde in single boards at different depths during the hot pressing treatment stage, thereby promoting the rapid release of formaldehyde remaining in the single boards.

[0016] 2. The present application uses boron nitride powder as a filler, and introduces long alkyl chain compound ammonium stearate into the molecular structure of sodium silicate, thereby improving the thermal stability of the sodium silicate adhesive, and the solidified morphology is smoother; at the same time, nano-silicon dioxide is used as a curing agent, and nano-graphene and sepiolite are used as skeleton materials to prepare nano-modified sodium silicate, wherein the nano-silicon dioxide and boron nitride are uniformly dispersed in the network structure formed by nano-graphene and sepiolite in the form of particles, so that the sodium silicate with long alkyl chain can be more stably connected with the network structure, and at the same time, the nano-silicon dioxide and boron nitride can be uniformly dispersed and stably adhered to the surface of the sodium silicate, forming a solidified adhesive that can be uniformly film-formed, thereby improving the bonding strength and thermal stability of the sodium silicate adhesive. DETAILED DESCRIPTION

[0017] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, the conventional products that can be purchased in the market are adopted.

[0018] The production process of the formaldehyde-free furniture plate provided by the embodiments of the present application will be described in detail below.

[0019] The production process of the formaldehyde-free furniture plate comprises the following steps:

[0020] S1. After cutting treatment, at least three veneers are dried to have a water content of 5-9%;

[0021] S2. One side of each of the two veneers located at the outermost side is uniformly coated with an adhesive, and the remaining middle layer veneers are completely immersed in the adhesive;

[0022] S3. One side of one middle layer veneer is attached to one outer side veneer which is coated with the adhesive, and then the first hot pressing treatment is performed, and then the temperature is lowered to 60-70 DEG C;

[0023] S4. Then, the remaining middle layer veneers are sequentially attached to the previous middle layer veneer, and each time a middle layer veneer is attached, the second hot pressing treatment is performed, and then the temperature is lowered to 70-80 DEG C;

[0024] S5. Then, one side of another outer side veneer which is coated with the adhesive is attached to the outer side of the attached middle layer veneer, and then the third hot pressing treatment is performed; the obtained plywood after hot pressing can be placed at room temperature for 18-24 hours; wherein the adhesive comprises, by weight fraction, 20-40 parts of modified sodium silicate, 5-10 parts of boron nitride powder and 1-5 parts of ammonium stearate.

[0025] In addition, the inventor found that in the prior art, when hot pressing the multi-layer plate, the plate is basically adhered one by one, and then hot pressing treatment is finally performed, so that the adhesion effect of the whole plate is not ideal, and even the phenomenon of glue opening may occur. The inventor innovatively proposes that each layer of plate is adhered one by one, and hot pressing treatment and temperature lowering are performed one by one, and the pressure during hot pressing is controlled. In this way, the adhesion between adjacent veneers can be more stable, and the formaldehyde in the adhesive or the plate and the bubbles that may exist in the adhesive can be removed. As the number of veneer layers increases, the hot pressing temperature increases to meet the adhesion strength between the veneers and to accelerate the movement of formaldehyde in the veneers at different depths during the hot pressing treatment stage, thereby promoting the rapid release of formaldehyde remaining in the veneers.

[0026] In the embodiment, the modified sodium silicate is modified by nano-silicon dioxide, nano-graphene and sepiolite, and the mass ratio of sodium silicate to nano-silicon dioxide, nano-graphene and sepiolite is 5-10:1-3:1-3:1-3; the preparation method of the modified sodium silicate is as follows: a certain amount of nano-silicon dioxide, nano-graphene and sepiolite are first dissolved in cetyltrimethylammonium bromide (the total mass of nano-silicon dioxide, nano-graphene and sepiolite is 15%), then twice the total mass of deionized water and twice the total mass of ethanol, sodium silicate and dispersant are added, and then water bath heating, strong stirring, oscillation dispersion and vacuum drying are carried out.

[0027] The present application uses boron nitride powder as filler, and introduces long alkyl chain compound ammonium stearate into the molecular structure of sodium silicate, thereby improving the thermal stability of the sodium silicate adhesive, and the solidified morphology is smoother; meanwhile, nano-silicon dioxide is used as a curing agent, and nano-graphene and sepiolite are used as skeleton materials to prepare nano-modified sodium silicate, wherein the nano-silicon dioxide and boron nitride are uniformly dispersed in the network structure formed by nano-graphene and sepiolite in a particle state, so that the sodium silicate with long alkyl chains can be more stably connected with the network structure, and at the same time, the nano-silicon dioxide and boron nitride can be uniformly dispersed and stably adhered on the surface of the sodium silicate, forming a solidified adhesive that can be uniformly formed into a film, thereby improving the bonding strength and thermal stability of the sodium silicate adhesive.

[0028] In the embodiment, the preparation method of the adhesive is as follows: the mixture of phosphate powder and boric acid powder is uniformly mixed with boron nitride powder (mass ratio 1:1:2), and then added to an ammonium stearate solution, stirred for a period of time, and then the mixed solution is added to a modified sodium silicate aqueous solution (volume ratio of mixed solution to modified sodium silicate aqueous solution is 1-1.5:2), and then placed at room temperature for a period of time after high-speed stirring for 0.5-1.5 h under the condition of 50-80℃ to obtain the adhesive.

[0029] In the embodiment, the first heat pressing treatment is performed at a heat pressing pressure of 2-3 MPa and a temperature of 120-140℃; the second heat pressing treatment is performed at a heat pressing pressure of 3-3.5 MPa and a temperature of 140-170℃; and the third heat pressing treatment is performed at a heat pressing pressure of 3.5-4.1 MPa and a temperature of 170-200℃.

[0030] In the embodiment, the heat pressing treatment is performed as follows:

[0031] (1) When the heat pressing plate of the heat pressing machine is quickly closed to approach the plate blank, the oil supply amount of the oil cylinder of the heat pressing machine is reduced, so that the closing speed of the heat pressing plate is slowed down, and the plate blank is slowly pressed to avoid airflow impact on the plate blank; when the oil supply amount of the oil cylinder is reduced, the heat pressing plate continues to press downward due to its own weight and downward acceleration, the volume of the oil cylinder is expanded, and a short-time pressure drop is caused; when the oil supply amount catches up, the pressure continues to rise;

[0032] (2) Then, first low pressure pressurization, and then high pressure pressurization, that is, first pressurization by the low pressure energy tank, so that the pressure is about 1 / 3-1 / 2 of the set pressure, and then pressurization by the high pressure energy tank, so that the pressure reaches the set pressure. The purpose of using two energy tanks is to ensure that the pressure can be continuously and stably increased to the set pressure in a short time in a relay manner during pressurization. Then, the pressure is kept constant for 10-30 min. The main role is to make the surface layer of the blank more tightly pressed, and the glue film rapidly melts, levels, solidifies and reaches a certain strength under high temperature and high pressure, so that multiple single boards are tightly bonded into a whole;

[0033] (3) Finally, the hot press plate is quickly unloaded and lifted. The main purpose is to quickly reduce the pressure of the board after hot pressing, so that the adhesive between the single board and the surface layer has completed the solidification and combination into a whole, and the hot press plate is quickly unloaded and lifted to avoid the board being under high temperature and high pressure for a long time, which reduces the physical and chemical properties of the adhesive.

[0034] Example 1

[0035] A formaldehyde-free furniture board production process, comprising the following steps:

[0036] S1. After cutting treatment of four single boards (first single board, second single board, third single board, fourth single board bonded in turn), drying, so that the water content is 8%;

[0037] S2. One side of the first single board and the fourth single board located at the outermost side is evenly brushed with adhesive, and the second single board and the third single board in the middle layer are completely immersed in the adhesive;

[0038] S3. Then, one side of the second single board is bonded with the side of the first single board brushed with adhesive, and hot pressing treatment is carried out: hot pressing pressure 2.5 MPa, temperature 130℃, and then cooling to 65℃; when the hot press plate is quickly closed to approach the blank, the oil inlet amount of the hot press oil cylinder is reduced, the closing speed of the hot press plate is slowed down, and the blank is slowly pressed during the control of the hot pressing pressure; then, first low pressure pressurization, and then high pressure pressurization, that is, first pressurization by the low pressure energy tank, so that the pressure is about 1.2 MPa of the set pressure, and then pressurization by the high pressure energy tank, so that the pressure reaches 2.5 MPa; then, the pressure is kept constant for 10-30 min; finally, the hot press plate is quickly unloaded and lifted;

[0039] S4. Then, the third single board is bonded with the second single board, and hot pressing treatment is carried out: hot pressing pressure 3 MPa, temperature 150℃, and then cooling to 75℃, and the pressure adjustment of the hot pressing operation is the same as S3;

[0040] S4. Then the third veneer is attached to the other side of the second veneer, and heat pressing treatment is performed: heat pressing pressure 3.8 MPa, temperature 180℃, the heat pressing operation is adjusted in the same way as S3; then it can be used after standing at room temperature for 18-24h;

[0041] The adhesive comprises, by weight fraction, 30 parts of modified sodium silicate, 8 parts of boron nitride powder, and 3 parts of ammonium stearate; the preparation method is as follows: a mixture of sodium phosphate powder and boric acid powder is uniformly mixed with boron nitride powder (mass ratio 1:1:2), added to an ammonium stearate solution, stirred for a period of time, then the mixed solution is added to a modified sodium silicate aqueous solution (volume ratio of the mixed solution to the modified sodium silicate aqueous solution is 1-2), stirred at high speed for 1h at 70℃, and then solidified after standing at room temperature for a period of time to obtain the adhesive;

[0042] The modified sodium silicate is modified by nano-silicon dioxide, nano-graphene, and sepiolite, and the mass ratio of sodium silicate to nano-silicon dioxide, nano-graphene, and sepiolite is 7:2:2:1; the preparation method is as follows: nano-silicon dioxide, nano-graphene, and sepiolite are first dissolved in cetyltrimethylammonium bromide (15% of the total mass of nano-silicon dioxide, nano-graphene, and sepiolite), then twice the total mass of deionized water and twice the total mass of ethanol are added, sodium silicate and dispersant OP-10 are added, heated in a constant-temperature water bath at 80℃ for 2h, then subjected to strong stirring and oscillation dispersion, and then vacuum dried to obtain the modified sodium silicate.

[0043] Example 2

[0044] The difference between this embodiment and Example 1 is that:

[0045] A formaldehyde-free furniture board production process, comprising the following steps:

[0046] S1. After cutting treatment, dry the three veneers (first veneer, second veneer, and third veneer which are sequentially bonded) to a moisture content of 8%;

[0047] S2. Uniformly brush the adhesive on one side of the first veneer and the third veneer which are located at the outermost sides, and completely immerse the second veneer in the middle layer in the adhesive;

[0048] S3. Then attach one side of the second veneer to the side of the first veneer which is brushed with the adhesive, and perform the first heat pressing treatment: heat pressing pressure 2.5 MPa, temperature 130℃, and then reduce the temperature to 65℃;

[0049] S4. Then attach the third veneer to the other side of the second veneer, and perform the second heat pressing treatment: heat pressing pressure 3 MPa, temperature 150℃, and then reduce the temperature to 75℃; then it can be used after standing at room temperature for 18-24h.

[0050] Example 3

[0051] The difference between the embodiment and embodiment 1 is that the adhesive comprises modified sodium silicate 25 parts, boron nitride powder 5 parts, and ammonium stearate 5 parts by weight.

[0052] Example 4

[0053] The difference between the embodiment and embodiment 1 is that the adhesive comprises modified sodium silicate 40 parts, boron nitride powder 10 parts, and ammonium stearate 4 parts by weight.

[0054] Example 5

[0055] The difference between the embodiment and embodiment 1 is that the modified sodium silicate comprises sodium silicate, nano-silicon dioxide, nano-graphene and sepiolite in a mass ratio of 6:2:2:1.

[0056] Comparative Example 1

[0057] The difference between the comparative example and embodiment 1 is that the adhesive comprises modified sodium silicate 10 parts, boron nitride powder 15 parts, and ammonium stearate 0.1 parts by weight.

[0058] Comparative Example 2

[0059] The difference between the comparative example and embodiment 1 is that the sodium silicate is not modified.

[0060] Comparative Example 3

[0061] The difference between the comparative example and embodiment 1 is that the first single board, the second single board, the third single board and the fourth single board are sequentially attached and then subjected to a heat pressing treatment.

[0062] Experimental Example 1

[0063] The board materials prepared in examples 1-5 and comparative examples 1-3 are denoted as test board materials 1-8; and the related properties thereof are tested, and the results are shown in Table 1.

[0064] Table 1-Board material performance results

[0065] Test group Formaldehyde release / mg / L Internal bond strength / Mpa Taber bond strength / Mpa 1 0.18 1.3-1.4 1.4-1.5 2 0.20 1.3-1.4 1.4-1.6 3 0.17 1.3-1.4 1.4-1.5 4 0.17 1.3-1.4 1.4-1.5 5 0.18 1.3-1.4 1.4-1.5 6 0.39 1.0-1.1 1.1-1.2 7 0.43 0.8-0.9 0.9-1.0 8 0.42 0.7-0.8 0.8-0.9

[0066] As shown in the data in Table 1, the board material obtained by using the board material production process provided in the embodiment has good aldehyde removal effect, and more importantly, has strong adhesion capacity, better mechanical strength and thermal stability.

[0067] The above only provides preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the production of a formaldehyde-free furniture board, characterized in that, The method comprises the following steps: S1. After cutting treatment, dry at least three veneers to have a water content of 5-9%; S2. Uniformly brush the adhesive on one side of each of the two veneers at the outermost side, and completely immerse the remaining middle layer veneers in the adhesive; S3. Attach one middle layer veneer to one outer side veneer by brushing the adhesive on one side of the middle layer veneer, and then perform first hot pressing treatment, and then cool down; S4. Then, sequentially attach the remaining middle layer veneers to the previous middle layer veneer, and perform second hot pressing treatment after attaching each middle layer veneer, and then cool down; S5. Then, attach the other outer side veneer to the outer side of the attached middle layer veneers by brushing the adhesive on one side of the other outer side veneer, and then perform third hot pressing treatment; and the obtained plywood can be obtained after standing at room temperature for 18-24 hours; The adhesive comprises modified sodium silicate 20-40 parts by weight, boron nitride powder 5-10 parts by weight, and ammonium stearate 1-5 parts by weight. The modified sodium silicate is modified by nano-silicon dioxide, nano-graphene and sepiolite. The preparation method of the adhesive comprises the following steps: uniformly mixing a mixture of phosphate powder and boric acid powder with boron nitride powder, adding the mixture into a modified sodium silicate aqueous solution, stirring at a high speed for 0.5-1.5 hours at 50-80°C, and then standing at room temperature for a period of time to solidify. In the first hot pressing treatment, the hot pressing pressure is 2-3 MPa and the temperature is 120-140°C; in the second hot pressing treatment, the hot pressing pressure is 3-3.5 MPa and the temperature is 140-170°C; and in the third hot pressing treatment, the hot pressing pressure is 3.5-4.1 MPa and the temperature is 170-200°C.

2. The formaldehyde-free furniture board production process according to claim 1, characterized in that, In the modified sodium silicate, the mass ratio of sodium silicate to nano-silicon dioxide, nano-graphene and sepiolite is 5-10:1-3:1-3:

1.

3. The formaldehyde-free furniture board production process according to claim 2, characterized in that, The preparation method of the modified sodium silicate comprises the following steps: dissolving a certain amount of nano-silicon dioxide, nano-graphene and sepiolite, suspending the mixture, heating and stirring in a water bath, then adding sodium silicate and a dispersing agent, and then performing strong stirring, oscillation and dispersion, and vacuum drying.

4. The formaldehyde-free furniture board production process according to claim 1, characterized in that, In the hot pressing treatment, (1) when the hot pressing plate of the hot pressing machine is quickly closed to approach the blank, the closing speed of the hot pressing plate is slowed down, and the blank is slowly pressed; (2) then, low-pressure pressing is performed first, and then high-pressure pressing is performed, and the pressure is kept unchanged; (3) finally, the pressure is quickly released and the hot pressing plate is lifted.

5. The formaldehyde-free panel production process for furniture according to claim 4, characterized in that, In step (2), the pressure during low-pressure pressing is 1 / 3-1 / 2 of the set pressure.