SPC floor substrate processing technology and introduction of problems

SPC floor is a new type of environmentally friendly floor developed based on high technology. It has the characteristics of zero formaldehyde, mildew proof, moisture proof, fire proof, insect proof, and simple installation.

SPC floor is made by extruder combined with T-die to extrude PVC substrate. Three-roll, four-roll or five-roll calender is used to separate PVC wear-resistant layer, PVC color film and PVC substrate with one-time heating and bonding. The patterned product has a simple process, the fitting is completed by heat, and no glue is needed.

SPC floor materials use environmentally friendly formulas, do not contain harmful substances such as heavy metals, phthalates, methanol, etc., and comply with EN14372, EN649-2011, IEC62321, and GB4085-83 standards. It is very popular in developed countries in Europe and America and the Asia-Pacific market.

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SPC floor main performance requirements

1. It has lower shrinkage, warpage and better toughness.

2. Ensure that it is not easy to be deformed and has a good locking tension under various environments and a certain peeling force between the substrate and the film. The performance is mainly determined by the ability of the processing technology and equipment of the material types and components.

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Processing requirements

1. Due to the relatively large extrusion volume of the SPC floor production line and the need for online laminating, the stability of continuous production is very important.

2. Because the SPC floor is highly filled, the screw is worn out and the screw value is relatively high, so the impact of screw life on the total cost must be considered.

3. The floor is relatively thin, the thickness tolerance is small, and the extrusion speed is fast, so it requires better material dispersion, plasticization performance and fluidity.

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Processing Equipment

1. Screw barrel with high wear resistance, relatively low extrusion pressure and better plasticization;

2. Design a reasonable mold with uniform discharge;

3. Multi-roll calendering system with simple operation and adjustment and precise thickness control;

4. The film guide tension control system is accurate and reliable;

5. And have enough cooling space and capacity;

6. Cutting and moving should not adversely affect the appearance and warpage of the board;

7. Manufacturer's selection: You can't pursue output one-sidedly, but choose the size of the machine according to the thickness of your own sheet. 80/92/110 is suitable for the production of plates with different thickness ranges. Generally, it is reasonable to configure 1:2:1 or 1:3:1.

(The size of the extruder and the thickness of the plate should be reasonably matched)

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Recipe points

1. PVC resin: adopts ethylene method five type resin, which has good strength and toughness and is environmentally friendly.

2. The fineness of calcium powder: Because the addition ratio is large, it will directly affect the formulation cost, processing performance, wear of the screw barrel and product performance, so it is not possible to choose too coarse calcium powder. The fineness of calcium powder should be 400-800 mesh. .

3. Internal and external lubrication: Considering the long residence time of the material in the extruder at high temperature, as well as the performance of the material and the factors of peeling force, it is recommended to use high-performance wax to control the small amount of use, and use different waxes to meet the initial and mid-to-long term Lubrication requirements.

4. ACR: Due to the high content of calcium powder in the SPC floor and high plasticization requirements, in addition to the control of screw type and processing technology, additives must be added to help plasticize and ensure that the melt has a certain strength and is in the rolling process. There is a certain degree of malleability.

5. Toughening agent: The floor not only needs low shrinkage, good rigidity, but also a certain degree of toughness. It needs to balance rigidity and toughness to ensure the firmness of the lock, not to soften at high temperatures, and to maintain at low temperatures. A certain degree of resilience.

CPE has good toughness, but a large amount of addition reduces the rigidity of PVC, the Vicat softening temperature, and causes the shrinkage rate to increase.

6. Dispersant: Since there are many components and the addition ratio of calcium carbonate is relatively large, the infiltration and dispersion treatment of calcium carbonate and the dispersion of the components are very important. Dispersion can not only improve the processing performance but also improve the product performance, increase the mold removal cycle, reduce and delay the wear of the screw barrel.

PE wax is not only a lubricant, but also has a dispersing effect, but the added amount will affect the balance of internal and external lubrication, the melt strength will become worse, and the shrinkage of the product will be increased, the peeling force will be reduced, and the product will become brittle. Other dispersants: fluorinated compounds, isocyanate compounds, small amount, good effect, not only play a dispersing role but also a coupling lubricating role, but the price is high.

7. Recycled materials: Try to use the company's production recycled materials and post-processed recycled materials.

Note: clean, not damp, crushed and blended in batches and then ground. In particular, the recycled materials from the slitting slot must be blended and ground in proportion to form a closed recycled material for recycling. The large change in the added amount of return material requires sample adjustment process formula.

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Processing technology and control

1. Formula and weighing

For materials of different weights, a weighing instrument with corresponding accuracy is required to ensure the accuracy of weighing.

Material integration: It is convenient to store, weigh, and transfer materials, and needs to be sampled to check the components and accuracy. If it is an automatic weighing system, monitoring and review is also required.

2. Mixed material storage

Feeding order: The feeding order is determined according to the feeding method.

The automatic feeding and mixing system can be set to: 90°C for filler, 95°C for treating agent and PVC resin, 105-110°C for stabilizer lubricant, 115°C for processing aid enhancer, and 120-125°C for return material.

Manual feeding: PVC resin + filling material + small material + PVC resin + filling material + PVC resin + return material; one-time feeding, discharge at 120-125°C.

Cold mixing: It must be cooled quickly enough to prevent material deterioration, and it has the ability to cool to 40-45°C.

Storage: In order to ensure the uniformity of the material, it is necessary to store it in a large storage tank and put it aside for a certain period of time before use.

To mix the materials that have been left for a certain period of time, it is necessary to detect the dry flow properties of different batches of materials, and to detect the rheological properties of the logistics, as a monitoring method, and provide a basis for analysis and improvement.

Note that there are differences in mixing effects between different mixers, as well as differences in mixing temperature and time.

3. Extrusion process

The setting of processing technology not only affects the processing level, but also affects product quality and production efficiency. It needs to be considered comprehensively in combination with equipment characteristics, material properties, and formulas.

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The size of the extruder is related to the product specifications. The size of the extruder has a certain relationship with the size of the product section.

1. First of all, under a certain extrusion speed of the extruder, the production line speed is already very fast, the molding pressure is relatively high, and the plasticization and fluidity of the material are required to be high. If the production depends on the opening of the die gap, the longitudinal stretching will be relatively large. , It has high requirements for melt strength, and because of the stretching orientation, it is easy to cause a large difference in the shrinkage rate in the vertical and horizontal directions, causing the shrinkage rate to exceed the standard and the sheet warping. At the same time, high-speed production also requires high cooling for calendering and bonding.

If the 110/135 extrusion line is used to produce flooring, the formulation process should be carefully designed and set up.

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According to the current situation: the gap between the die is slightly larger than the thickness of the floor.

Body: The temperature in the first zone and the second zone is very important, and it is necessary to ensure that the plasticization is convenient for vacuuming. Too high, easy to accumulate material in the vacuum port, generally between 185-195 ℃, others can be slightly lower.

The temperature of the confluence core has a great influence on the back pressure. A lower temperature is beneficial for the melt to change from spiral motion to linear motion, generally 165-175°C.

The mold temperature is relatively higher, which is conducive to the flow of small gap melt. Generally, it is between 190-200℃, and the thickness of the blank is adjusted to be uniform in combination with the mold gap.

Rotation speed of extruder main engine: generally controlled at 75-85% of rated speed. The feeding speed is mainly determined according to the speed of the host and the current of the host (load).

Under the premise of formula determination, the processing temperature, main engine speed, and feeding speed are matched with each other, so that the current is stable, the discharge is uniform, and the surface is free of defects, and there is a certain production speed.

The screw will wear out for a certain period of time. The processing technology can be adjusted first, such as reducing the extrusion speed, increasing the feeding speed, and appropriately increasing the processing temperature of the first and second zones to reduce the temperature of the confluence core. Adjust the formula appropriately to increase the amount of ACR. If necessary, re-adjust the gaps related to the screw barrel, sand and polish the damaged parts, and then adjust the process formula.

4. Calendering and filming process

Under the premise of stable extrusion.

Main control: the matching of roller gap, temperature, speed, and front and back speed.

The gap and speed of the first pair of rollers determine the basic thickness of the floor, which should be preliminarily determined according to the linear speed of extrusion. The speed of the laminating roller at the back is slightly faster to ensure a certain amount of tension and not cause the film to stretch and narrow. The traction speed is so, so that the plate will not be deformed. According to the actual situation, some adjustments are slower. Embossing and filming are mainly determined by the roller gap and roller temperature. Different sheet thicknesses and film types use different gaps and temperatures, and take into account the influence of traction speed.

Roller gentle speed: It should be ensured that the calendering is normal, the embossing is clear, the film is firmly bonded, the trimming is sufficient, and the film is not deformed.

Roller temperature: generally 165-185°C.

The gap between the two pairs of rollers is basically the same. The two need to be adjusted together.

80 unit 4mm floor reference production process reference:

Hot mixing: 125°C

Cold mix: ≤45℃

Die gap: slightly smaller in the middle of 3.8～4.0

Host speed: 20rpm

Host current; 75A

Feeding speed: 10rpm

Calendering gap: 4mm

Roller temperature: 175℃

Roller and traction speed: 600 (table value)

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5. Stereotypes and others

Since the products in the production process have not been completely finalized, the cutting flow avoids stress, and the carrying tray needs to be firm and flat. Product testing also requires the substrate and finished products to be stored for a certain period of time for sampling.

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6. A brief analysis of common problems-poor product molding

A brief analysis of common problems

1) The product size is unstable, the shaping mold is not full of the mold, and the wall thickness is uneven

Reasons: unreasonable internal and external lubrication of the formula, unstable quantitative feeding speed, serious wear of the screw barrel, and incorrect matching clearance;

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Solution: Improve the ratio of internal and external lubricants, correct feeding failures, replace the barrel and screw, and adjust the gap between the barrel and screw.

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2) The appearance of the product is uneven, the color deviation is obvious, and the surface has irregular fish scales; the product performance is poor; the toughness is poor, the product is brittle, and the impact resistance is unqualified

Reason: the formula structure is unreasonable, the inorganic filling is too high, the plasticization is not good, and the amount of impact material is insufficient;

Solution: Modify the formula structure, appropriately reduce the content of inorganic fillers, modify the material to be plasticized to about 65%, and increase impact-resistant materials as appropriate.

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3) The output of the finished product is bent, deformed, and partially sag

Reason: The machine head and the shaping die are not on the same plane, the extrusion speed is too fast, the cooling water temperature is too high, the water pressure is too low, the water flow is insufficient, the water and air path is not smooth, and the vacuum negative pressure is insufficient;

Solution: rectify the die and the setting die at the same level, reduce the extrusion speed & cooling water temperature, increase the water pressure and flow rate, adjust the vacuum negative pressure to check the smooth flow of the water and air paths.

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in conclusion

Only by fully understanding product quality and processing requirements, combining equipment and materials, rationally designing formulas and processing techniques, and mastering their functions and their mutual relationships and influences, can we balance product quality, production efficiency, formulation costs, and processing costs. Elements.

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