Urea-melamine-formaldehyde resin for light wood recombination material as well as preparation method and application of urea-melamine-formaldehyde resin

Abstract

The invention discloses urea-melamine-formaldehyde resin for a light wood recombined material as well as a preparation method and application of the urea-melamine-formaldehyde resin. The urea-melamine-formaldehyde resin comprises the following components: 90-135 parts of a formaldehyde aqueous solution; 55 to 75 parts of urea; 35 to 45 parts of melamine; 3-6 parts of a modifier 1; 0.5 to 1.5 parts of morpholine; and 1-2 parts of a modifier 2. According to the invention, the self-made urea-melamine-formaldehyde resin is used as an adhesive for preparing the light wood recombined material, and the wood recombined material is low in density, light in weight and good in water resistance; and wood recombined materials with various colors or colors can be prepared according to requirements, so that the application range of the wood recombined materials is greatly widened.

Description

Technical Field

[0001] The invention belongs to the technical field of wood processing, and in particular relates to a urea-melamine-formaldehyde resin for lightweight wood recombinant materials and a preparation method and application thereof. Background Art

[0002] Wood reconstructed materials are boards or square materials made by processing wood into wood reconstructed units (wood bundles, fiberized wood veneers, thin veneers), applying glue, and then drying, paving, hot pressing and other processes. At present, the hot pressing method is used to prepare wood reconstructed materials. The resin used is mainly low molecular weight phenolic resin for impregnation. The resin has good permeability. The prepared wood reconstructed materials have good water resistance and strong weather resistance. They are widely used in decoration, building exterior walls, outdoor floors, plank roads and other fields.

[0003] To ensure that the wood reconstituted material has high water resistance and weather resistance, the pressing density of the material is usually controlled at 1.0g / cm 3 However, the obtained wood reconstructed materials have high density and hardness. When used, especially as structural materials, the heavy weight brings many inconveniences to the application. When used as indoor floors or furniture, the high hardness of the board surface makes it easier to cause falls or bumps; the board is too heavy, which is not conducive to its application in the field of interior decoration. In addition, the adhesive used to prepare the wood reconstructed material is phenolic resin, which has a dark color and is difficult to make light-colored or colorful wood reconstructed materials, which limits the application expansion of the material. Summary of the invention

[0004] In order to solve the above technical problems, the object of the present invention is to provide a urea-melamine-formaldehyde resin for lightweight wood recombinant materials and a preparation method and application thereof.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a urea-melamine-formaldehyde resin for a lightweight wood recombinant material, comprising the following components in parts by weight:

[0007]

[0008] Preferably, the mass concentration of the formaldehyde aqueous solution is 37-55%.

[0009] Preferably, the modifier 1 is sodium carbonate or sodium bicarbonate, or a mixture of the two.

[0010] Preferably, the modifier 2 is ammonium carbonate or ammonium bicarbonate, or a mixture of the two.

[0011] The urea-melamine-formaldehyde resin for light wood recombinant materials provided by the present invention has a viscosity of 100mPa·s-300mPa·s and a solid content of 55%-65%.

[0012] The urea-melamine-formaldehyde resin for lightweight wood recombinant materials provided by the present invention has a short heating and curing time without adding a curing agent, has certain foaming performance during the curing process, can fill the gaps between wood recombinant units during the preparation of lightweight wood recombinant materials, make the recombinant material board surface flat, and at the same time reduce the entry of water, reduce the water absorption and expansion rate of the board, so that the board has good water resistance and weather resistance, and can meet the requirements for indoor recombinant material use.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned urea-melamine-formaldehyde resin for lightweight wood recombinant materials, comprising the following steps:

[0014] (1) Add the formaldehyde aqueous solution and the first batch of urea into the reactor, adjust the pH to 7-9, and keep the temperature at 80-90° C. for 20-40 minutes;

[0015] (2) adjusting the pH to 2.5-3.5, continuing to keep warm for 2-3 hours, adding the first batch of modifier 1, the first batch of melamine and the second batch of urea, and keeping warm at 80-90° C. for 1-2 hours;

[0016] (3) adding the second batch of modifier 1 and the second batch of melamine, and continuing to keep the temperature at 80-90° C. for 1-2 hours;

[0017] (4) adding morpholine and the third batch of urea, keeping the temperature at 55-65° C. for 30-60 minutes, cooling, adding modifier 2 at 30-40° C., stirring for 20-40 minutes, and obtaining urea-melamine-formaldehyde resin for lightweight wood recombinant materials.

[0018] In the process of the present invention, urea is added in three batches, the first batch of urea is used in an amount of 30-40 parts, the second batch of urea is used in an amount of 10-20 parts, and the third batch of urea is used in an amount of 5-15 parts; melamine is added in two batches, the first batch of melamine is used in an amount of 15-25 parts, and the second batch of melamine is used in an amount of 10-20 parts; modifier 1 is added in two batches, the first batch of modifier 1 is used in an amount of 2-4 parts, and the second batch of modifier 1 is used in an amount of 1-2 parts.

[0019] In a third aspect, the present invention provides a lightweight wood recombinant material, which is formed by stacking a plurality of wood recombinant units along the grain, and a resin layer composed of the above-mentioned urea-melamine-formaldehyde resin for the lightweight wood recombinant material is arranged between and within the wood recombinant units, and the resin layer has a porous structure.

[0020] The wood recombinant unit of the present invention has a diameter of 0.5-1.2 mm and a density of 0.40-0.75 g / cm 3 .

[0021] The wood recombinant unit of the present invention is one or more of poplar, basswood, sycamore, alder, kapok and fir.

[0022] In a fourth aspect, the present invention further provides a method for preparing the above-mentioned lightweight wood reconstituted material, comprising the following steps:

[0023] (I) Preparation of wood recombinant units:

[0024] The wood is processed into wood fiber bundles with a diameter of ≤1.7mm by using a deflaking device;

[0025] (II) Drying of wood recombinant units:

[0026] The prepared wood fiber bundle is dried by a drying device to a moisture content of 3-8% at a drying temperature of 80-110°C;

[0027] (III) Gluing of wood recombinant unit:

[0028] Put the wood recombinant unit into a high-pressure glue dipping tank filled with urea-melamine-formaldehyde resin for light wood recombinant materials to apply glue, and the amount of glue applied is 10-20wt%;

[0029] (IV) Recombination unit assembly:

[0030] Laying the wooden recombinant unit on a paving table along the grain, with the number of paving layers being 10-30 layers;

[0031] (V) Hot pressing of recombinant materials:

[0032] The laid reconstructed material slab is sent into the hot press and hot pressed using the "cold in-cold out" process.

[0033] Preferably, in step (v), the hot pressing parameters are: hot pressing temperature 105-125° C., hot pressing time 30-60 minutes, hot pressing pressure 0.5 MPa-3.0 MPa.

[0034] Compared with the prior art, the present invention has the following excellent effects:

[0035] The present invention uses sodium carbonate and / or sodium bicarbonate, ammonium carbonate and / or ammonium bicarbonate, and morpholine as modifiers to synthesize a self-curing (no curing agent required) and foaming urea-melamine-formaldehyde resin, which is used as an adhesive to prepare a lightweight wood reconstructed material. The wood reconstructed material has low density, light weight, and good water resistance.

[0036] The present invention uses light-colored urea-melamine-formaldehyde resin as an adhesive to prepare a wood recombinant material, and can prepare wood recombinant materials of various colors or colors according to needs, which greatly broadens the application range of the wood recombinant material;

[0037] The wood reconstituted material prepared by the invention is green and environmentally friendly, has strong processability, can be used without facing, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a diagram showing the state of the resin after curing and the test diagram of the curing height in Example 1;

[0039] Figure 2 This is a graph showing the state of the resin after curing and the test graph of the curing height of Comparative Example 1;

[0040] Figure 3 The surface (left) and end (right) images of the wood reconstituted material prepared in Example 4;

[0041] Figure 4 This is an enlarged end view of the wood reconstituted material prepared in Example 4;

[0042] Figure 5 The surface (left) and end (right) images of the wood reconstituted material prepared in Comparative Example 4;

[0043] Figure 6 This is an enlarged end view of the wood reconstituted material prepared in Comparative Example 4. DETAILED DESCRIPTION

[0044] The present invention is further described below by means of specific implementation methods. The following examples are specific implementation methods of the present invention, but the implementation methods of the present invention are not limited to the following examples.

[0045] The raw materials used in the examples and comparative examples of the present invention are all commercially available.

[0046] Example 1: Preparation of urea-melamine-formaldehyde resin for lightweight wood recombinant materials

[0047] 115 kg of 44% formaldehyde aqueous solution and 40 kg of urea are added to a reaction kettle, the pH is adjusted to 8.0, the mixture is kept at 85°C for 30 minutes, the pH is adjusted to 3.0, the mixture is kept at 85°C for 2.5 hours, 3 kg of sodium carbonate, 25 kg of melamine and 10 kg of urea are added, the mixture is kept at 85°C for 1.5 hours, 1.5 kg of sodium carbonate and 15 kg of melamine are added, the mixture is kept at 85°C for 1.5 hours, 1 kg of morpholine and 10 kg of urea are added, the mixture is kept at 60°C for 45 minutes, the mixture is cooled, 1.5 kg of ammonium carbonate is added at 35°C, the mixture is stirred for 30 minutes, and a urea-melamine-formaldehyde resin for a light wood recombinant material is obtained. The resin has a viscosity of 200 mPa·s, a solid content of 60%, a curing time of 9.42 minutes, and a curing height of 77 mm.

[0048] Example 2: Preparation of urea-melamine-formaldehyde resin for lightweight wood recombinant materials

[0049] 135 kg of 37% formaldehyde aqueous solution and 30 kg of urea are added to a reaction kettle, the pH is adjusted to 7.0, the mixture is kept at 80°C for 40 minutes, the pH is adjusted to 2.5, the mixture is kept at 80°C for 2 hours, 4 kg of sodium bicarbonate, 25 kg of melamine and 20 kg of urea are added, the mixture is kept at 80°C for 2 hours, 2 kg of sodium bicarbonate and 20 kg of melamine are added, the mixture is kept at 80°C for 2 hours, 0.5 kg of morpholine and 5 kg of urea are added, the mixture is kept at 55°C for 60 minutes, the mixture is cooled, 2 kg of ammonium bicarbonate is added at 40°C, the mixture is stirred for 40 minutes, and a urea-melamine-formaldehyde resin for a light wood recombinant material is obtained. The resin has a viscosity of 100 mPa·s, a solid content of 55%, a curing time of 11.32 minutes, and a curing height of 65 mm.

[0050] Example 3: Preparation of urea-melamine-formaldehyde resin for lightweight wood recombinant materials

[0051] 100 kg of 50% formaldehyde aqueous solution and 40 kg of urea were added to a reactor, the pH was adjusted to 9.0, the mixture was kept at 90°C for 20 minutes, the pH was adjusted to 3.5, the mixture was kept at 90°C for 3 hours, 2 kg of sodium carbonate, 15 kg of melamine and 20 kg of urea were added, the mixture was kept at 90°C for 1 hour, 1 kg of sodium carbonate and 20 kg of melamine were added, the mixture was kept at 90°C for 1 hour, 1.5 kg of morpholine and 15 kg of urea were added, the mixture was kept at 55°C for 60 minutes, the mixture was cooled, 1 kg of ammonium carbonate was added at 30°C, the mixture was stirred for 20 minutes, and urea-melamine-formaldehyde resin for light wood recombinant materials was obtained. The resin had a viscosity of 300 mPa·s, a solid content of 65%, a curing time of 7.83 minutes, and a curing height of 83 mm.

[0052] Comparative Example 1: Urea-melamine-formaldehyde resin without modifier 1, modifier 2 and morpholine

[0053] 115 kg of 44% formaldehyde aqueous solution and 40 kg of urea were added to a reactor, the pH was adjusted to 8.0, the mixture was kept at 85°C for 30 minutes, the pH was adjusted to 3.0, the mixture was kept at 85°C for 2.5 hours, 25 kg of melamine and 10 kg of urea were added, the mixture was kept at 85°C for 1.5 hours, 15 kg of melamine was added, the mixture was kept at 85°C for 1.5 hours, 10 kg of urea was added, the mixture was kept at 60°C for 45 minutes, the temperature was lowered, and urea-melamine-formaldehyde resin without modifier 1, modifier 2 and morpholine was obtained. The resin had a viscosity of 210 mPa·s, a solid content of 59%, a curing time of 63.67 minutes, and a curing height of 10 mm.

[0054] Comparative Example 2: Urea-melamine-formaldehyde resin without modifier 2 and morpholine

[0055] 115 kg of 44% formaldehyde aqueous solution and 40 kg of urea were added to a reactor, the pH was adjusted to 8.0, the mixture was kept at 85°C for 30 minutes, the pH was adjusted to 3.0, the mixture was kept at 85°C for 2.5 hours, 3 kg of sodium carbonate, 25 kg of melamine and 10 kg of urea were added, the mixture was kept at 85°C for 1.5 hours, 1.5 kg of sodium carbonate and 15 kg of melamine were added, the mixture was kept at 85°C for 1.5 hours, 10 kg of urea was added, the mixture was kept at 60°C for 45 minutes, the temperature was lowered, and urea-melamine-formaldehyde resin without modifier 2 and morpholine was obtained. The resin had a viscosity of 210 mPa·s, a solid content of 60%, a curing time of 45.58 minutes, and a curing height of 23 mm.

[0056] Comparative Example 3: Urea-melamine-formaldehyde resin without morpholine

[0057] 115 kg of 44% formaldehyde aqueous solution and 40 kg of urea were added to a reaction kettle, the pH was adjusted to 8.0, the mixture was kept at 85°C for 30 minutes, the pH was adjusted to 3.0, the mixture was kept at 85°C for 2.5 hours, 3 kg of sodium carbonate, 25 kg of melamine and 10 kg of urea were added, the mixture was kept at 85°C for 1.5 hours, 1.5 kg of sodium carbonate and 15 kg of melamine were added, the mixture was kept at 85°C for 1.5 hours, 10 kg of urea was added, the mixture was kept at 60°C for 45 minutes, the mixture was cooled, 1.5 kg of ammonium carbonate was added at 35°C, the mixture was stirred for 30 minutes, and urea-melamine-formaldehyde resin without morpholine was obtained. The resin had a viscosity of 215 mPa·s, a solid content of 60%, a curing time of 33.23 minutes, and a curing height of 34 mm.

[0058] Example 4: Lightweight poplar wood recombinant material

[0059] The lightweight poplar wood recombinant material of the embodiment of the present invention is formed by stacking 20 layers of poplar wood recombinant units along the grain, and the urea-melamine-formaldehyde resin prepared in Example 1 is arranged between and inside the recombinant units. The diameter of the recombinant unit is 1.0 mm, and the density of the recombinant material is 0.50 g / cm 3 The specific preparation method is as follows:

[0060] (I) Preparation of wood recombinant units:

[0061] The poplar wood is processed into a poplar wood fiber bundle with a diameter of 1.4 mm by using a deflaking device;

[0062] (II) Drying of wood recombinant units:

[0063] The prepared poplar fiber bundle is dried in a constant temperature oven to a moisture content of 5% at a drying temperature of 95°C;

[0064] (III) Gluing of wood recombinant unit:

[0065] The poplar wood recombinant unit is placed in a high-pressure dipping tank filled with the urea-melamine-formaldehyde resin prepared in Example 1 for dipping, and the amount of the dipping agent is 15 wt %;

[0066] (IV) Recombination unit assembly:

[0067] Laying the poplar wood recombinant unit flat on a paving table along the grain, with 20 layers of paving;

[0068] (V) Hot pressing of recombinant materials:

[0069] The paved poplar wood recombinant material slab is sent into the hot press machine and hot pressed using the "cold in-cold out" process. The hot pressing parameters are: hot pressing temperature 115℃, hot pressing time 45 minutes, hot pressing pressure 1.5Mpa, and the lightweight poplar wood recombinant material can be obtained.

[0070] Figure 3 and Figure 4 The surface, end surface and end surface enlarged view of the light poplar wood prepared in this embodiment are shown. It can be seen from the figure that the prepared poplar wood reconstructed material has a smooth surface, a dense end surface, and the reconstructed unit is filled with resin.

[0071] Example 5: Lightweight basswood reconstituted material

[0072] The lightweight basswood recombinant material of the embodiment of the present invention is formed by stacking 15 layers of basswood recombinant units along the grain, and the urea-melamine-formaldehyde resin prepared in Example 3 is arranged between and within the recombinant units. The diameter of the recombinant unit is 1.2 mm, and the density of the prepared basswood recombinant material is 0.75 g / cm 3 The specific preparation method is as follows:

[0073] (I) Preparation of wood recombinant units:

[0074] The basswood is processed by a debonding device to produce basswood fiber bundles with a diameter of 1.7 mm;

[0075] (II) Drying of wood recombinant units:

[0076] The prepared basswood fiber bundle is dried in a chain oven to a moisture content of 8% at a drying temperature of 80°C;

[0077] (III) Gluing of wood recombinant unit:

[0078] The basswood recombinant unit is placed in a high-pressure dipping tank filled with urea-melamine-formaldehyde prepared in Example 3 for dipping, and the amount of glue applied is 20wt%;

[0079] (IV) Recombination unit assembly:

[0080] Laying the basswood recombinant unit along the grain on a paving table, with 10 layers of paving;

[0081] (V) Hot pressing of recombinant materials:

[0082] The laid basswood reconstructed material slab is sent into the hot press and hot pressed using the "cold in-cold out" process. The hot pressing parameters are: hot pressing temperature 125°C, hot pressing time 30 minutes, hot pressing pressure 3.0Mpa, and lightweight basswood reconstructed material can be obtained.

[0083] Example 6: Lightweight Paulownia wood reconstituted material

[0084] The lightweight paulownia wood recombinant material of the embodiment of the present invention is formed by stacking 30 layers of paulownia wood recombinant units along the grain, and the urea-melamine-formaldehyde resin prepared in Example 2 is arranged between and inside the recombinant units. The diameter of the recombinant unit is 0.5 mm, and the density of the recombinant material is 0.40 g / cm 3 The specific preparation method is as follows:

[0085] (I) Preparation of wood recombinant units:

[0086] The paulownia wood is processed into a paulownia wood fiber bundle with a diameter of 1.0 mm by using a deflaking device;

[0087] (II) Drying of wood recombinant units:

[0088] The prepared sycamore wood fiber bundle was dried in a constant temperature oven to a moisture content of 3% at a drying temperature of 110°C;

[0089] (III) Gluing of wood recombinant unit:

[0090] The sycamore wood recombinant unit is placed in a high-pressure dipping tank filled with urea-melamine-formaldehyde prepared in Example 2 for dipping, and the amount of glue applied is 10wt%;

[0091] (IV) Recombination unit assembly:

[0092] Laying the wooden recombinant unit on a paving table along the grain, with 30 layers of paving;

[0093] (V) Hot pressing of recombinant materials:

[0094] The laid reconstructed material slab is sent into the hot press and hot pressed using the "cold in-cold out" process. The hot pressing parameters are: hot pressing temperature 105°C, hot pressing time 60 minutes, hot pressing pressure 0.5Mpa, and the lightweight paulownia wood reconstructed material can be obtained.

[0095] Example 7: Lightweight Alder Reconstructed Material

[0096] Same as Example 4, except that the recombinant unit is alder fiber bundle, and the density of the obtained light alder recombinant material is 0.6 g / cm 3 .

[0097] Example 8: Lightweight Kapok Wood Reconstructed Material

[0098] Same as Example 4, except that the recombinant unit is a kapok fiber bundle, and the density of the obtained light kapok recombinant material is 0.5 g / cm 3 .

[0099] Example 9: Lightweight fir wood reconstituted material

[0100] Same as Example 4, except that the recombinant unit is a fir fiber bundle, and the density of the obtained light fir recombinant material is 0.45 g / cm 3 .

[0101] Comparative Example 4: Poplar wood reconstituted material prepared by urea-melamine-formaldehyde resin without adding modifier 1, modifier 2 and morpholine

[0102] The same as Example 4, except that the urea-melamine-formaldehyde resin without modifier 1, modifier 2 and morpholine prepared in Comparative Example 1 was used for sizing, and the density of the obtained poplar wood reconstituted material was 0.68 g / cm 3 .

[0103] Figure 5 and Figure 6 The poplar wood reconstructed material prepared by impregnation with phenolic resin in Comparative Example 4 is shown to have an uneven surface, many end surface gaps, and no resin filling between the wood reconstructed units.

[0104] Comparative Example 5: Poplar wood reconstituted material prepared by urea-melamine-formaldehyde resin without adding modifier 2 and morpholine

[0105] The same as Example 4, except that the urea-melamine-formaldehyde resin without modifier 2 and morpholine prepared in Comparative Example 2 was used for sizing, and the density of the obtained poplar wood reconstituted material was 0.64 g / cm 3 .

[0106] Comparative Example 6: Poplar wood reconstituted material prepared by urea-melamine-formaldehyde resin without adding morpholine

[0107] The same as Example 4, except that the urea-melamine-formaldehyde resin without morpholine prepared in Comparative Example 3 was used for sizing, and the density of the obtained poplar wood reconstituted material was 0.68 g / cm 3 .

[0108] Comparative Example 7: Basswood reconstituted material prepared by impregnation with phenolic resin

[0109] Same as Example 5, except that the phenolic resin (solid content of 58%, viscosity of 80 mPa·s) was used for impregnation, and the density of the obtained basswood reconstituted material was 0.82 g / cm 3 .

[0110] Performance test standards or methods:

[0111] The viscosity of the resin is tested in accordance with GB / T 14074-2017 "Test methods for adhesives and resins for wood industry 3.3";

[0112] The solid content of the resin is tested in accordance with GB / T 14074-2017 "Test methods for adhesives and resins for wood industry 3.5";

[0113] The curing time and curing height of the resin are tested according to the following operation: 5 g of the resin is weighed and placed in a Φ15 mm×150 mm test tube, the test tube is placed in a preheated 115°C polyethylene glycol liquid, the timing is started, and a Φ7 mm×300 mm glass rod is used to slowly stir until the stirring rod suddenly cannot be lifted or the resin suddenly hardens, the timing is stopped and the glass test tube is taken out, and the time is recorded, which is the curing time of the resin; the distance between the upper surface of the cured resin in the test tube and the bottom of the test tube is measured, and the height is recorded, which is the curing height of the resin (such as Figure 1 and Figure 2 The results are shown in Table 1;

[0114] The density of wood reconstituted materials shall be tested in accordance with GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels 4.2";

[0115] The water absorption thickness expansion rate of wood reconstituted materials is tested in accordance with GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels 4.4", and the absorption thickness expansion rate is ≤10%.

[0116] The appearance color was observed by naked eyes. The results are shown in Table 2.

[0117] Table 1 Urea-melamine-formaldehyde resin performance results

[0118] Detection Viscosity (mPa·s) Solid content Curing time (minutes) Curing height (mm) Example 1 200 60％ 9.42 77 Example 2 100 55％ 11.32 65 Example 3 300 65％ 7.83 83 Comparative Example 1 210 59％ 63.67 10 Comparative Example 2 210 60％ 45.58 23 Comparative Example 3 215 60％ 33.23 34

[0119] As can be seen from Table 1, the resins prepared in Examples 1-3 of the present invention have a short curing time without adding a curing agent, and the height of the resin after curing is large. The resins prepared in Comparative Examples 1-3 of the present invention have a long curing time, and the height of the resin after curing is small, indicating that the urea-melamine-formaldehyde resin for lightweight wood recombinant materials prepared in the present invention has a certain self-curing property, and can foam during the curing process.

[0120] Table 2 Performance results of wood reconstituted materials

[0121] Test items <![CDATA[Density (g / cm 3 )]]> Water absorption thickness expansion rate (%) Appearance Color Example 4 0.50 7.68 Wood color Example 5 0.75 5.67 Wood color Example 6 0.40 8.43 Wood color Example 7 0.60 6.24 Wood color Example 8 0.50 6.87 Wood color Example 9 0.45 7.15 Wood color Comparative Example 4 0.68 15.52 Wood color Comparative Example 5 0.64 13.50 Wood color Comparative Example 6 0.68 11.47 Wood color Comparative Example 7 0.75 10.53 Reddish brown

[0122] By comparing Example 4 with Comparative Examples 4-6, it can be seen that the urea-melamine-formaldehyde resin synthesized by using sodium carbonate and / or sodium bicarbonate, ammonium carbonate and / or ammonium bicarbonate and morpholine as modifiers is used as an adhesive to prepare a lightweight wood reconstructed material, and the wood reconstructed material has low density, light weight and good water resistance. The results show that sodium carbonate and / or sodium bicarbonate, ammonium carbonate and / or ammonium bicarbonate and morpholine have a synergistic effect.

[0123] From the comparison between Example 5 and Comparative Example 7, it can be seen that although the two wood reconstructed materials have the same density, the water absorption expansion rate of the wood reconstructed material obtained in Example 5 is significantly lower than that of Comparative Example 7, that is, the light wood reconstructed material prepared in Example 5 has better water resistance and is more suitable for preparing light wood reconstructed materials. In addition, the color of the reconstructed material prepared in Example 5 is log color, the color of the wood reconstructed material prepared in Comparative Example 7 is reddish brown, and the color of the wood reconstructed material prepared in Example 5 is lighter. The results show that compared with the existing impregnation phenolic resin, the urea-melamine-formaldehyde resin prepared by the present invention as an adhesive for preparing low-density wood reconstructed materials has good water resistance and light color.

Claims

1. A urea-melamine-formaldehyde resin for lightweight wood recombinant materials, characterized in that: By weight, it includes the following components: 90-135 parts of formaldehyde aqueous solution Urea 55-75 parts 35-45 parts of melamine Modifier 1 3-6 parts Morpholine 0.5-1.5 parts Modifier 2 1-2 parts.

2. The urea-melamine-formaldehyde resin for lightweight wood recombinant materials according to claim 1, characterized in that: The mass concentration of the formaldehyde aqueous solution is 37-55%.

3. The urea-melamine-formaldehyde resin for lightweight wood recombinant materials according to claim 1, characterized in that: The modifier 1 is sodium carbonate or sodium bicarbonate or a mixture of the two; the modifier 2 is ammonium carbonate or ammonium bicarbonate or a mixture of the two.

4. The method for preparing urea-melamine-formaldehyde resin for lightweight wood recombinant materials according to any one of claims 1 to 3, characterized in that: The steps include: (1) Add the formaldehyde aqueous solution and the first batch of urea into the reactor, adjust the pH to 7-9, and keep it at 80-90°C for 20-40 minutes; (2) Adjust the pH to 2.5-3.5, keep warm for 2-3 hours, add the first batch of modifier 1, the first batch of melamine and the second batch of urea, and keep warm at 80-90°C for 1-2 hours; (3) Add the second batch of modifier 1 and the second batch of melamine, and continue to keep the temperature at 80-90°C for 1-2 hours; (4) Add morpholine and the third batch of urea, keep the temperature at 55-65°C for 30-60 minutes, cool down, add modifier 2 at 30-40°C, stir for 20-40 minutes, and obtain urea-melamine-formaldehyde resin for lightweight wood recombinant materials.

5. The method for preparing urea-melamine-formaldehyde resin for lightweight wood recombinant materials according to claim 4, characterized in that: The first batch of urea is used in an amount of 30-40 parts, the second batch of urea is used in an amount of 10-20 parts, and the third batch of urea is used in an amount of 5-15 parts; the first batch of melamine is used in an amount of 15-25 parts, and the second batch of melamine is used in an amount of 10-20 parts; The amount of the first batch of modifier 1 is 2-4 parts, and the amount of the second batch of modifier 1 is 1-2 parts.

6. A lightweight wood reconstituted material, characterized in that: It is composed of several wood recombinant units stacked along the grain, and a resin layer composed of urea-melamine-formaldehyde resin for lightweight wood recombinant materials according to any one of claims 1 to 3 is arranged between and inside the wood recombinant units, and the resin layer is a porous structure.

7. The lightweight wood reconstituted material according to claim 6, characterized in that: The wood recombinant unit has a diameter of 0.5-1.2 mm and a density of 0.40-0.75 g / cm 3 .

8. The lightweight wood reconstituted material according to claim 6, characterized in that: The wood recombinant unit is one or more of poplar, basswood, sycamore, alder, kapok and fir.

9. The method for preparing a lightweight wood recombinant material according to any one of claims 6 to 8, characterized in that: The steps include:

1. Preparation of wood recombinant units: The wood is processed into wood fiber bundles with a diameter of ≤1.7mm by using a deflaking device; (II) Drying of wood recombinant units: The prepared wood fiber bundle is dried by drying equipment to a moisture content of 3-8% at a drying temperature of 80-110°C; (III) Gluing of wood recombinant units: The wood recombinant unit is placed in a high-pressure glue dipping tank filled with urea-melamine-formaldehyde resin for light wood recombinant materials to apply glue, and the amount of glue applied is 10-20wt%; (IV) Recombination unit assembly: Laying the wooden recombinant unit on a paving table along the grain, with the number of paving layers being 10-30 layers; (V) Hot pressing of recombinant materials: The laid reconstructed material slab is sent into the hot press and hot pressed using the "cold in-cold out" process.

10. The method for preparing a lightweight wood recombinant material according to claim 9, characterized in that: In step (v), the hot pressing parameters are: hot pressing temperature 105-125° C., hot pressing time 30-60 minutes, hot pressing pressure 0.5 MPa-3.0 MPa.

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