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Comprehensively analyze the performance requirements and main quality indicators of Phenolic Film coated plywood base paper (referred to as plywood base paper).
The performance requirements of Phenolic Film coated plywood base paper (referred to as plywood base paper) were comprehensively analyzed, and its main quality indicators were given. The two typical production processes currently in the factory were also discussed and studied, with a view to providing some reference and guidance to manufacturers of plywood base paper and those developing the product. Building formwork is a model plate used in the construction industry to construct concrete buildings. According to different materials, it is divided into steel formwork, plastic formwork, and laminated formwork. Compared with steel formwork, coated formwork has the advantages of low price, acid and alkali corrosion resistance, and smooth surface; Compared to plastic plywoods, it has the advantages of low price, excellent expansion and contraction rates, and small coefficient of thermal expansion and contraction. Currently, Phenolic Film coated formwork has been used in the construction of shear walls, vertical wall panels, viaducts, dams, beams, columns, tunnels, and other buildings, and its share is increasing. Therefore, the demand for plywood paper used for the production of Phenolic Film coated formwork is clearly increasing, with broad prospects for development.
plywood paper is obtained by impregnating plywood base paper with water-based phenolic resin or melamine resin glue. However, there are no unified national and industrial standards for plywood base paper. Most enterprises determine whether the product is qualified or unqualified based on their own technical indicators. The product quality on the market varies greatly, and sometimes there are significant differences in the quality of different batches of products from the same manufacturer, This has brought great difficulties to the manufacturers of plywood paper and plywoods; On the other hand, through preliminary market and technical research, the author also learned that most manufacturers of plywood base paper are small in scale and lack scientific research conditions and foundation. In the process of independently exploring and developing plywood base paper products, there are inevitably many detours. In this article, we conducted research and a large number of development trials on plywood base paper
Thoroughly and comprehensively analyze the properties of the plywood base paper based on the inspection work
Can request, and conduct research and discussion on the current two typical production processes, with a view to playing a role in guiding plywood base paper manufacturers in formulating production processes and improving product quality.
Performance requirements for base paper for Phenolic Film coated formwork
1.1 Performance requirements for plywood base paper
plywood base paper has no specific requirements for whiteness indicators, so the fiber raw materials for producing plywood base paper can be chemical pulp, mechanical pulp, high yield pulp, or waste pulp. Currently, many factories use waste as new materials
Smell paper as raw material to reduce production costs. Required for plywood base paper
The main performance includes the following aspects.
(1) In the range of 60 to 70 gm -, the uniformity of the quantitative distribution is also very important, that is, good uniformity. Otherwise, when impregnating the glue solution, the absorption is uneven, resulting in uneven paper surface after drying, which affects the next process. Even if the adhesive is applied, clouds or spots will appear on the surface of the building plywood after high temperature and hot pressing, resulting in a decline in the product grade.
(2) Good absorbency, mainly due to the fact that the impregnated glue is a water-based phenolic resin or melamine resin, resulting in good absorption
The raw material is an important guarantee for the smooth processing of the plywood base paper. main
The surface absorbency of the plywood base paper was measured using Cobb method and combined with two methods of water absorption height to jointly evaluate the absorbency of the plywood base paper.
(3) Strength performance is also crucial for plywood base paper, including dry tensile strength (longitudinal) and wet tensile strength retention (longitudinal), which can be expressed as strength indicators using tensile strength. If the strength of the plywood base paper is poor, on the one hand, it can lead to paper breakage before or during the dipping process, affecting the continuity of production and reducing production efficiency; On the other hand, it directly affects the strength of the impregnated plywood paper, which in turn affects the strength of the coated plywood.
(4) The expansion ratio should be small. The elasticity of paper reflects the size of the paper when its moisture content changes. The smaller the paper’s elasticity, the better the shape stability of the paper when its moisture content decreases or increases. For plywood base paper, the lateral expansion ratio is particularly important and cannot be too large. This is mainly due to the fact that during the process from the base paper of the plywood to the production of the laminated plywood, it is necessary to successively undergo processing procedures such as dipping, drying, slitting, leveling, and high-temperature and high-pressure bonding. The temperature and humidity of the paper vary greatly. If the lateral shrinkage of the paper during this process is too large, it will directly lead to difficulties in slitting, and it is difficult to ensure the accuracy of high-temperature and high-pressure bonding.
1.2 Main quality indicators of plywood base paper
Table 1 lists the main performance test results of two commercial plywood base paper samples, numbered plywood Base Paper I and plywood Base Paper II. The plywood base paper I is produced in Dezhou, Shandong Province, and the plywood base paper II is produced in Tangshan, Hebei Province. Based on this and in combination with the actual use of these two types of plywood base paper in the construction industry, the main quality index ranges of plywood base paper are listed in Table 1 for reference only. two
Production Process Analysis of Base Paper for Architectural Laminated plywood
2.1 Analysis of the production process of plywood base paper in a paper mill in Northeast China
The pulping process of this factory is mainly aimed at obtaining higher tensile strength and smaller lateral shrinkage.
Fiber material ratio: It requires not only good fiber strength, but also long average fiber length and good flexibility. So fiber
Raw material ratio: larch wood pulp: red and white pine wood pulp: birch wood pulp
=35%: 35%: 30% (all based on absolute dry mass) of selected fibrinogen
All materials are home-made pulp.
Beating process: Two 450 cone mills are used for coniferous wood pulp
Continuous beating with a 450 disc mill, with a beating concentration of 3.3% to 3.8%, a beating degree of (21 ± 2) SR and a wet weight of (12+2.0) g. The hardwood pulp is beaten using a volt beater with a beating concentration of 5.0% to 5.5% and a beating degree of (38+2) SR wet weight of (35+0.2) g. Beating degree of mixed slurry in the pulp mixing tank (26+3) ° SR wet weight (10 ± 2.0) go
Paper machine manufacturing conditions: add wet strength agent in the high level box, add rosin gum in the mixing box, control the temperature rise curve during drying, and make the wet strength agent partially mature. The temperature of the drying cylinder from the first cylinder to the eighth cylinder is: 53 ℃/78 ℃ 91/103 ℃ 958890 ℃
The compactness of the plywood base paper is 06~0.7gcm, the longitudinal tensile strength is ≥ 90N, and the lateral shrinkage is ≤ 1.5%. Obviously, its tightness and longitudinal tensile resistance are both greater than those of the two commercial paper samples in Table 1, resulting in a high paper strength, and a significantly smaller lateral shrinkage rate than those of the two commercial paper samples. However, the disadvantage of this process is that rosin sizing is also added, and the Cobb value reaches 35-40gm. The author believes that this will affect the absorbability of the base paper to the glue liquid, that is, the glue liquid is not fully absorbed, and when making a Phenolic Film coated plywood, the plywood paper and the plywood are not firmly bonded, which is prone to delamination. Therefore, it is not recommended to apply glue to the plywood base paper.
2.2 Analysis of the production process of plywood base paper in a paper mill in Shandong Province
This factory uses waste newsprint pulp as raw material. Due to the lack of specific requirements for whiteness of plywood base paper, there is no need for deinking treatment for waste newsprint. Instead, it only needs to be pulped and then processed for pulping and papermaking.
Compared to a paper mill in Northeast China, the cost of raw materials is lower and the production process is simpler. The process conditions are as follows: the beating degree of the finished pulp is 38~42 ° SR, and the main method of beating is to use a wire splitting broom. Try to avoid fiber cutting; Online concentration: 0.6%~0.7%; The online pH value of the base paper produced by the above method is very close to the test results in Table 1 in terms of quantity, tightness, water absorption height, and lateral shrinkage, which are also within the reference quality index range. However, the longitudinal tensile strength is only 25N, which clearly shows a low strength. This is due to the fact that the raw material is completely waste pulp, resulting in a relatively low paper strength. It is suggested that there are three ways to solve the problem
Decision: First, adjust the beating process and select the appropriate beating degree; second, award
Add an appropriate amount of dry strength agent inside, and ensure that the adding position and method of the reinforcing agent are correct; Adding a suitable proportion of chemical pulp and mixing it with waste pulp can improve the strength of the paper. In addition, the addition amount of wet strength agent generally does not exceed 2%, but in this process, the addition amount of wet strength agent reaches and exceeds 3.7%. Whether this will have a negative impact on the repulping performance of plywood paper base paper needs further research. 3600~4000 yuan. Considering the reduction of production costs, most of them use full waste pulp as raw material, and the strength of the paper is relatively poor
Paper breakage is easy to occur, so it is very necessary to improve the strength of the base paper for Phenolic Film coated formwork. In addition, there is a dilemma of difficult recycling and degradation of construction film coated plywood paper. How to solve this problem from the production process of plywood base paper, impregnation glue, impregnation process, and other aspects? Producing green and environmentally friendly construction film coated plywood paper will be a need for sustainable development and should be the focus of research and development of this paper in the future.
