Blockboard making process using fir as core board
2024-05-05 06:06:45
As a kind of better performance board, blockboard has the characteristics of stable structure, not easy to deform, large format, beautiful board surface, good mechanical properties and high quality wood. Domestic demand for it is large and it is very popular in the market. There are two main types of blockboards in the Zhejiang market: one is the Cunninghamialanceolata core of the Chinese fir, and the other is the Populusspp. The poplar core blockboard is mainly from Jiangsu and Shandong, and the fir core blockboard is mainly from Jiangsu and Zhejiang. According to market research, the main problem existing in blockboard manufacturers is that the resulting blockboard has large warpage deformation and low strength. The main reason is that the factory produces blockboards based on experience and has not systematically and scientifically studied and Look for more suitable process conditions and ignore the most basic production theories and principles. This topic combines the problems of a certain blockboard manufacturer in Zhejiang, and the physical properties, warpage deformation and bubbling of blockboard are carried out on the amount of core strip coating, core sheet hot pressing temperature and core strip moisture content and uniformity. The specific research aims to develop a better manufacturing process of Chinese fir core board to reduce costs and improve production efficiency without reducing the performance of blockboard [1~5].
1 Test materials and methods
1. 1 Test material core strip: The core strip adopts Chinese fir, and the length, width and thickness are 450mm×40mm×17mm, and the average moisture content is 125%. It requires no large tree tumor and no bark. Medium plate: The middle plate is made of Liuan Parashoreastellata veneer with a web size of 450mm×450mm and a thickness of 1 60mm. Back panel: Oumanmanaucoumeaklaineeana veneer with a web size of 450mm x 450mm and a thickness of 0 6mm. Adhesive: A urea-formaldehyde resin adhesive having a solid content of 460 g·kg -1 was used, and the amount of the curing agent (ammonium chloride) was 10 g·kg -1 .
2 Test methods
2 .1 Preparation of core board After the planed fir core strip is coated with urea-formaldehyde resin glue, put it into a metal frame, apply a lateral pressure through the bolt, feed it into a 100t flat press, operate according to different experimental conditions, hot pressing After the end, sanding with sandpaper removes the surface contamination of the core board and adjusts the thickness deviation of the core board. Note that the direction of the annual rings of adjacent fir strips should be reversed when glued. The basic process conditions: the amount of glue applied (single side) is 80g·m-2, the hot pressing temperature is 140°C, and the moisture content of the core strip is 10%. The single factor experiment was performed with time-invariant conditions referring to the basic process. The experiment was repeated three times.
2 .2 Blockboard is made in the blank, the middle plate and the panel should be facing outward, and the fiber direction of each layer should be perpendicular to each other. When feeding into the hot press, the hot pressing temperature is 100 ° C, the hot pressing time is 5 min, and the hot pressing pressure is 0 9 MPa. When the blank is formed, the amount of the surface plate is 150g·m-2, and the amount of curing agent is 10g·kg-1.
2. 3 Test piece detection The core strip test is carried out according to the conventional method. When the blockboard is sampled, since the size of the test piece is too small, it cannot be sampled according to the provisions of GB5849 1999. Instead, it is carried out as follows: first cut off the edge of the test plate by 25 cm, and then take six pieces of transverse static bending strength. . The transverse static bending strength was measured according to GB5849 1999.
2 Results and analysis
2. The effect of the amount of core strip coating on the performance of blockboard can be drawn from Table 1. As the amount of sizing increases, the static bending strength increases from 22 3 MPa to 25 9 MPa. The increase of the amount of sizing means that more chemical groups per unit area of ​​the fir strips participate in the reaction, and the greater the bonding force, the greater the bonding force between the fir strips. Because the buckling board is mostly broken between the fir strip and the fir strip, the greater the joint between the fir strips, the better the bending resistance of the blockboard, that is, the greater the static bending strength. However, as can be seen from Table 1, the amount of sizing increased from 80 g·m -2 to 200 g·m -2 , and the degree of increase in static bending strength was not large. From an economic point of view, the amount of sizing increased by 200 g·m-2 from 80 g·m-2, and the production cost increased significantly. Therefore, from the perspective of performance and economics of the board, the amount of glue applied is preferably 80g·m-2.
2 The influence of the hot pressing temperature of the core board on the performance of the blockboard is shown in Table 1. The hot pressing temperature is increased from 100 ° C to 140 ° C, and the static bending strength is increased from 22 9 MPa to 27 3 MPa. The higher the temperature, the higher the activity of the group between the glue and the glue, so the glue strength increases, and the greater the bonding force between the fir strips, the greater the static bending strength. However, when the temperature is 180 °C, the static bending strength decreases. Because the wood evaporates at 120-150 °C, the water does not change much. The pre-carbonization occurs at 150-170 °C, and the strength decreases. The urea-formaldehyde resin glue is easy to produce at 180 °C. Pre-curing or over-curing eventually leads to a decrease in the strength of the static bending. During the experiment, it was found that when the core plate hot pressing temperature was 180 ° C, the core plate was easy to bubble when the press opening control was not good. Even if the pressure plate opening control is good, the resulting blockboard warpage deformation is serious, which may be related to the excessive hot pressing temperature, the shrinkage stress of the core plate from the press cooling and the stress imbalance in the plate. If the temperature is too high, the surface of the core plate obtained is more serious, such as poor sanding quality. When the core board is attached to the veneer, the middle plate is easily separated from the core plate. In short, when making the core board, the hot pressing temperature should not be too high, preferably 140 ° C.
3 The effect of moisture content on the performance of Chinese fir strips is shown in Table 2. When the moisture content of Chinese fir strips increased from 4% to 12%, the static bending strength increased. The moisture content of the Chinese fir strip is too low. The coated Chinese fir strip quickly absorbs the moisture in the glue. After the fir strip is placed in the press, the glue loses moisture, the fluidity is poor, the group activity is reduced, so the glue is poor. The static bending strength is low. With the increase of moisture, when the curing of the rubber in the Chinese fir strips creates an optimal moisture content range, the fluidity of the rubber is greatly enhanced. Due to the solvent action of water, the activity of some groups is increased and the adhesion is increased. The glue force increases and the static strength of the final plate increases. However, when the water content is increased from 12% to 20%, it can be seen from Table 2 that as the water content increases, the static bending strength of the blockboard decreases. When the moisture of the Chinese fir strip is too high, the moisture content of the cedar strip is too high, and the adhesive easily penetrates into the fir strip to affect the bonding strength. Moreover, when hot pressing, more gas is generated in the core sheet, which is easy to cause bubbling. During the course of the experiment, when the water content was 16% and 20%, bubbling occurred due to improper operation. Therefore, in general, the moisture content of Chinese fir strips is between 8% and 12%, which is not suitable for too low or too high.
3 The influence of the moisture content uniformity on the performance of the core strips used a total of 18 fir core strips. In the experiment, three kinds of plates were made, in which the moisture content of the 18 core strips of the No. 1 core plate was about 10%, the No. 2 core plate had 9 moisture content average 8%, and the 9 moisture content averaged 12%. The No. 3 plate has a moisture content of 6%, 6 of 10%, and 6 of 14%. The results show that the performance of the three boards is not much different. The static bending strength value is between 26 and 28 MPa, but the appearance is different. The appearance of the No. 1 plate is flat, the warpage is almost 0, the warpage of the No. 2 plate is 0 3%, and the warpage of the No. 3 plate is 0 8%. It can be seen from these data that the uniformity of the moisture content of the core strip has a great influence on the warpage of the blockboard. In a board, if there is no inconsistency in the various parts of the board, then the amount of expansion of the board is different during hot pressing, and the amount of vaporized vapor is different. The vapor pressure varies from place to place. The shrinkage is different everywhere, and the combined effect causes the residual stress in the plate to be inconsistent, so the warpage of the plate is generated. In the actual production, we must pay attention to the uniformity of the moisture content of the core material. When producing the same batch of plates, the raw materials should come from the same batch, while drying, while making the strip. After doing the above experiments, the experimental results were fed back to a certain manufacturer. After a manufacturer adjusted the production process appropriately and paid attention to the uniformity of the moisture content of the raw materials, the overall performance of the resulting blockboard was improved. A certain economic benefit.
4 Conclusion
Making cedar rubber blockboard, the moisture content of Chinese fir strip is 8%~12%. Moreover, the core strips in the same core sheet should have a uniform water content, otherwise the core sheets coming out are not flat, and finally the warp deformation of the blockboard is caused. The amount of sizing of the Chinese fir strip is preferably 80g·m-2. Too low a strength difference, too high will lead to an increase in cost. The suitable temperature for the hot pressing of the rubber is 140 ° C. The excessive temperature causes the surface of the core plate to be carbonized, so that the middle plate and the core plate are not glued well, and are easily separated and peeled off.
1 Test materials and methods
1. 1 Test material core strip: The core strip adopts Chinese fir, and the length, width and thickness are 450mm×40mm×17mm, and the average moisture content is 125%. It requires no large tree tumor and no bark. Medium plate: The middle plate is made of Liuan Parashoreastellata veneer with a web size of 450mm×450mm and a thickness of 1 60mm. Back panel: Oumanmanaucoumeaklaineeana veneer with a web size of 450mm x 450mm and a thickness of 0 6mm. Adhesive: A urea-formaldehyde resin adhesive having a solid content of 460 g·kg -1 was used, and the amount of the curing agent (ammonium chloride) was 10 g·kg -1 .
2 Test methods
2 .1 Preparation of core board After the planed fir core strip is coated with urea-formaldehyde resin glue, put it into a metal frame, apply a lateral pressure through the bolt, feed it into a 100t flat press, operate according to different experimental conditions, hot pressing After the end, sanding with sandpaper removes the surface contamination of the core board and adjusts the thickness deviation of the core board. Note that the direction of the annual rings of adjacent fir strips should be reversed when glued. The basic process conditions: the amount of glue applied (single side) is 80g·m-2, the hot pressing temperature is 140°C, and the moisture content of the core strip is 10%. The single factor experiment was performed with time-invariant conditions referring to the basic process. The experiment was repeated three times.
2 .2 Blockboard is made in the blank, the middle plate and the panel should be facing outward, and the fiber direction of each layer should be perpendicular to each other. When feeding into the hot press, the hot pressing temperature is 100 ° C, the hot pressing time is 5 min, and the hot pressing pressure is 0 9 MPa. When the blank is formed, the amount of the surface plate is 150g·m-2, and the amount of curing agent is 10g·kg-1.
2. 3 Test piece detection The core strip test is carried out according to the conventional method. When the blockboard is sampled, since the size of the test piece is too small, it cannot be sampled according to the provisions of GB5849 1999. Instead, it is carried out as follows: first cut off the edge of the test plate by 25 cm, and then take six pieces of transverse static bending strength. . The transverse static bending strength was measured according to GB5849 1999.
2 Results and analysis
2. The effect of the amount of core strip coating on the performance of blockboard can be drawn from Table 1. As the amount of sizing increases, the static bending strength increases from 22 3 MPa to 25 9 MPa. The increase of the amount of sizing means that more chemical groups per unit area of ​​the fir strips participate in the reaction, and the greater the bonding force, the greater the bonding force between the fir strips. Because the buckling board is mostly broken between the fir strip and the fir strip, the greater the joint between the fir strips, the better the bending resistance of the blockboard, that is, the greater the static bending strength. However, as can be seen from Table 1, the amount of sizing increased from 80 g·m -2 to 200 g·m -2 , and the degree of increase in static bending strength was not large. From an economic point of view, the amount of sizing increased by 200 g·m-2 from 80 g·m-2, and the production cost increased significantly. Therefore, from the perspective of performance and economics of the board, the amount of glue applied is preferably 80g·m-2.
2 The influence of the hot pressing temperature of the core board on the performance of the blockboard is shown in Table 1. The hot pressing temperature is increased from 100 ° C to 140 ° C, and the static bending strength is increased from 22 9 MPa to 27 3 MPa. The higher the temperature, the higher the activity of the group between the glue and the glue, so the glue strength increases, and the greater the bonding force between the fir strips, the greater the static bending strength. However, when the temperature is 180 °C, the static bending strength decreases. Because the wood evaporates at 120-150 °C, the water does not change much. The pre-carbonization occurs at 150-170 °C, and the strength decreases. The urea-formaldehyde resin glue is easy to produce at 180 °C. Pre-curing or over-curing eventually leads to a decrease in the strength of the static bending. During the experiment, it was found that when the core plate hot pressing temperature was 180 ° C, the core plate was easy to bubble when the press opening control was not good. Even if the pressure plate opening control is good, the resulting blockboard warpage deformation is serious, which may be related to the excessive hot pressing temperature, the shrinkage stress of the core plate from the press cooling and the stress imbalance in the plate. If the temperature is too high, the surface of the core plate obtained is more serious, such as poor sanding quality. When the core board is attached to the veneer, the middle plate is easily separated from the core plate. In short, when making the core board, the hot pressing temperature should not be too high, preferably 140 ° C.
3 The effect of moisture content on the performance of Chinese fir strips is shown in Table 2. When the moisture content of Chinese fir strips increased from 4% to 12%, the static bending strength increased. The moisture content of the Chinese fir strip is too low. The coated Chinese fir strip quickly absorbs the moisture in the glue. After the fir strip is placed in the press, the glue loses moisture, the fluidity is poor, the group activity is reduced, so the glue is poor. The static bending strength is low. With the increase of moisture, when the curing of the rubber in the Chinese fir strips creates an optimal moisture content range, the fluidity of the rubber is greatly enhanced. Due to the solvent action of water, the activity of some groups is increased and the adhesion is increased. The glue force increases and the static strength of the final plate increases. However, when the water content is increased from 12% to 20%, it can be seen from Table 2 that as the water content increases, the static bending strength of the blockboard decreases. When the moisture of the Chinese fir strip is too high, the moisture content of the cedar strip is too high, and the adhesive easily penetrates into the fir strip to affect the bonding strength. Moreover, when hot pressing, more gas is generated in the core sheet, which is easy to cause bubbling. During the course of the experiment, when the water content was 16% and 20%, bubbling occurred due to improper operation. Therefore, in general, the moisture content of Chinese fir strips is between 8% and 12%, which is not suitable for too low or too high.
3 The influence of the moisture content uniformity on the performance of the core strips used a total of 18 fir core strips. In the experiment, three kinds of plates were made, in which the moisture content of the 18 core strips of the No. 1 core plate was about 10%, the No. 2 core plate had 9 moisture content average 8%, and the 9 moisture content averaged 12%. The No. 3 plate has a moisture content of 6%, 6 of 10%, and 6 of 14%. The results show that the performance of the three boards is not much different. The static bending strength value is between 26 and 28 MPa, but the appearance is different. The appearance of the No. 1 plate is flat, the warpage is almost 0, the warpage of the No. 2 plate is 0 3%, and the warpage of the No. 3 plate is 0 8%. It can be seen from these data that the uniformity of the moisture content of the core strip has a great influence on the warpage of the blockboard. In a board, if there is no inconsistency in the various parts of the board, then the amount of expansion of the board is different during hot pressing, and the amount of vaporized vapor is different. The vapor pressure varies from place to place. The shrinkage is different everywhere, and the combined effect causes the residual stress in the plate to be inconsistent, so the warpage of the plate is generated. In the actual production, we must pay attention to the uniformity of the moisture content of the core material. When producing the same batch of plates, the raw materials should come from the same batch, while drying, while making the strip. After doing the above experiments, the experimental results were fed back to a certain manufacturer. After a manufacturer adjusted the production process appropriately and paid attention to the uniformity of the moisture content of the raw materials, the overall performance of the resulting blockboard was improved. A certain economic benefit.
4 Conclusion
Making cedar rubber blockboard, the moisture content of Chinese fir strip is 8%~12%. Moreover, the core strips in the same core sheet should have a uniform water content, otherwise the core sheets coming out are not flat, and finally the warp deformation of the blockboard is caused. The amount of sizing of the Chinese fir strip is preferably 80g·m-2. Too low a strength difference, too high will lead to an increase in cost. The suitable temperature for the hot pressing of the rubber is 140 ° C. The excessive temperature causes the surface of the core plate to be carbonized, so that the middle plate and the core plate are not glued well, and are easily separated and peeled off.
Ningbo Yinzhou Hengxi Winbate Household Product Manufacturer , https://www.winbatehousehold.com