Wood plywood phenolic glue

The production of glue has been around for hundreds of years and is mainly used in the leather industry. The main component of tannin is tannin, a natural polyphenolic compound with a large amount of active hydroxyl groups and carboxyl groups, which can replace phenol as a raw material for some industries. In the early 1990s, many research institutes in China carried out research on the use of plant tannins instead of phenol to obtain woodworking adhesives, including larch bark tannins and inkweed tannins.

In 1992, Nanjing Forestry University and Inner Mongolia Yakeshi Rubber Factory jointly developed tannin phenolic glue with larch bark rubber instead of 60% phenol, and applied it in the wood and bamboo plywood industry. Early application test results It shows that the bonding performance of tannin phenolic rubber with larch gum instead of 60% phenol is equivalent to that of traditional phenolic rubber, but the viscosity of the glue increases rapidly, the storage period of the glue is very short, and the process of coating is also not good.

In recent years, the formulation process has been improved and improved, and the liquid glue is made into powdered glue, thereby avoiding the self-polycondensation reaction during storage, so that the storage period of the adhesive is greatly extended, and packaging and transportation are also convenient. Laboratory studies have shown that this powdered larch tannin phenolic glue is easy to use and has good gluing properties.

2 Main performance indexes of powdered larch tannin phenolic glue

Appearance: Dark brown red powder Solid content: ≥ 90 %
Viscosity: 70 ~ 1 50s (coating - 4 cups 2 5 ° C)
Free phenol: ≤ 0.3% free formaldehyde: ≤ 0.2%
Can be bromide: ≥ 1 2 % water soluble multiple: 2 0
Storage period: 1 year or more pH value: 10.5~1 2

3 Application tests and results

3.1 Application on Pinus masson plywood formwork

3 . 1 . 1 Test conditions The test was carried out at the Jiangle Wood-based Panel Factory in Fujian Province. Specific test pieces:

1 Pinus masson veneer: thickness 2.0 mm, moisture content 8% ~ 10%.
2 Gluing process: Pour 40kg of warm water (water temperature about 50 °C) into the mixing cylinder, add 50kg of powdered larch tannin phenolic glue, stir for 20 minutes (stirring speed 1 50r min), then add 5kg of flour, stir Evenly.
3 Glued blank: The short core plate is coated on both sides with a glue amount of 2 3 0~2 50g m2; immediately after the glue is applied, the number of slab layers is 9 layers.
4 hot pressing: the slab directly enters the hot press without pre-pressing, hot pressing temperature: 1 40 ~ 1 45 ° C, unit pressure: 1.2 MPa, hot pressing time: 18 min.

3 . 1 . 2 Test results

Test batch: Specification 1 0 0 0mm × 2 0 0 0mm × 1 5mm A total of 46 sheets, counting 1.38 m3, a total of 50kg of powdered rubber was consumed. After the hot-pressed burrs were stacked for 25 hours, the edges were sawed and the test samples were randomly taken. The glue strength test is based on the concrete formwork plywood standard (GB9846.8-1 2). The test results are as follows:

The number of valid test pieces: 41, the number of qualified test pieces (gluing strength ≥0.8): 40, the number of unqualified test pieces: 1 Glue strength: Maximum value: 1.84MPa, minimum value: 0.78MPa, average value: 1. 1 6MPa, average wood breaking rate: 53%.

3.2 Application on poplar plywood formwork

3 . 2 . 1 Test conditions The test was carried out in Guannan Longhua Wood Industry Co., Ltd., Jiangsu Province. The specific conditions are:
1 poplar veneer: thickness of 1.8mm, short core board moisture content of 8%, long veneer moisture content of 10%.
2Adhesive process: Pour 22.5 kg of cold water into the mixing cylinder, add 25 kg of powdered larch tannin phenolic glue, stir for 5 min, place for 18 h, then add 2.5 kg of flour and mix well.
3 Glued blank: The short core plate is coated on both sides with a coating amount of 2 90g m2. The number of layers is 11 layers and the width is 91 5mm×1 83 0mm.
4 pre-pressure: unit pressure 0.8 MPa, time 1h.
5 hot pressing: hot pressing temperature 1 3 5~ 1 40°C, unit pressure 1.0 MPa, hot pressing time 18 8 3. 3 . 2 test results Random sampling, and according to concrete template with gluing standard (GB9846.8-1 2) Check the bonding strength, the results are as follows:
The number of valid test pieces: 3 6;
The number of qualified test pieces (gluing strength ≥0.7 MPa): 3 6;
Number of unqualified test pieces: 0.
Gluing strength: maximum: 1.69MPa; minimum: 0.96MPa;
Average value: 1.42 MPa; average wood breaking rate: 46%.

3 . 3 Application on poplar plywood box board

According to the requirements of Shanghai Bell Company, the poplar plywood used as the packing box has a thickness of 8mm, generally consists of 5-7 layers of veneers, requiring a white surface, a certain moisture resistance, low free phenol and free formaldehyde. In order to meet these requirements, laboratory tests were carried out with powdered larch tannin phenolic. The test conditions were:

(1) Poplar veneer: provided by Jiangsu Suqian Kangle Artificial Board Factory, the thickness of the surface plate is 1.0 mm, the thickness of the core plate is 1.65 mm, and the moisture content of the veneer is 9%;

(2) Glue ratio: The powdery glue and water are mixed and stirred in a ratio of 1:1 by weight.

(3) The amount of double-sided coating on the core board is: 200g/m2, 250g/m2, 300g/m2;

(4) The time of aging (stacking) of rubberized veneers is: 0, 30 min, 60 min, 90 min;

(5) Slab structure: 5 layers, the thickness of the blank is 5.95mm;

(6) The hot pressing temperatures are: 1 2 0 ° C, 130 ° C, 1 40 ° C; unit pressure: 1.2 MPa; hot pressing time: 6 min. After testing and analysis, the following conclusions can be drawn:

(1) The hot pressing temperature has a significant influence on the bonding strength. When the hot pressing temperature was 120 ° C, the bonding strength of all the test pieces was unacceptable. After the temperature rises to 130 °C, the bonding strength is obviously improved. The average bonding strength of the test piece with a coating amount of 200 g 2 is 0.82 MPa, the minimum value is 0.65 MPa, and the coating amount is 2 50 g. The average strength of the gluing strength of the test piece of m2 was 0.16 MPa. At a temperature of 1 40 ° C, the bonding strength is optimal.

(2) The influence of stacking and aging time of the veneer veneer on the bonding strength is highly significant. When the rubberized veneer is immediately pressed into the preform, the bonding strength is not satisfactory; after 30 minutes of aging, the gluing performance is remarkably improved.

(3) The amount of glue applied has a greater effect on the bonding strength, but the effect of increasing the amount of glue is not as good as increasing the hot pressing temperature and prolonging the aging time of the rubberized veneer.

(4) The amount of glue applied and the aging time of the rubberized veneer have a great influence on the surface quality (penetration). When the amount of glue is 200g/m2, the surface is basically free of pores; when the amount of glue is increased to 2 50g/m2, after 30 to 60 minutes of aging, the surface will not penetrate.

According to the above analysis results, the gluing process conditions of the poplar plywood box board are determined as follows: the weight ratio of the powdered glue to the water is 1:1, the veneer amount of the veneer is 2 50 g m2, and the veneer veneer is aged 3 to 60 min. , hot pressing temperature 130 ° C, unit pressure 12 MPa, hot pressing time (blank thickness 5.95 mm): 6 min.

According to the above process conditions, the application was promoted in Suqian Leisure Wood Factory in Suqian City, Jiangsu Province, Yangyang Sun Wood Co., Ltd. in Shuyang County, Jiangsu Province, and the Plywood Factory in Wuyang County, Jiangsu Province. It has been used in large quantities and its plywood The product supply was used by Shanghai Bell Company to make the packaging box, and the effect was good.

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