阅读说明：本技术 一种pvdc保鲜膜的制备方法 (Preparation method of PVDC preservative film ) 是由 王涛 陈智润 张弘 万宾华 李鹏飞 于 2019-09-27 设计创作，主要内容包括：本发明公开了一种PVDC保鲜膜的制备方法,通过对螺杆进行改进,使用低产能螺杆,挤出量控制在60kg/h～80kg/h,调整螺槽与螺筒之间的间隙为3.8～4.2mm,更有效的控制聚偏二氯乙烯熔融时的流速,有效解决保鲜膜碳化点、薄点等质量问题。使用此保鲜膜可以稳定密闭状态,有效提高包装的密合性,延长保鲜时间。采用铝合金轻型材料制成新型人字板,重量小,阻力小,最大张开度可达15cm,吨均破泡40.6kg。螺杆长径比1:18,进料压缩比1:3.5,使得连续运行周期由原来的运行周期40小时,到现在的110小时,提高效率和出品率,同时内在质量得到改善。(The invention discloses a preparation method of a PVDC preservative film, which is characterized in that a screw rod is improved, a screw rod with low productivity is used, the extrusion amount is controlled to be 60-80 kg/h, the gap between a screw groove and a screw cylinder is adjusted to be 3.8-4.2 mm, the flow rate of polyvinylidene chloride during melting is effectively controlled, and the quality problems of carbonization points, thin points and the like of the preservative film are effectively solved. The preservative film can be used for stabilizing a closed state, effectively improving the sealing property of packaging and prolonging the preservation time. The novel herringbone plate is made of aluminum alloy light materials, the weight is small, the resistance is small, the maximum opening degree can reach 15cm, and 40.6kg of bubbles are broken per ton. The length-diameter ratio of the screw is 1:18, and the feeding compression ratio is 1:3.5, so that the continuous operation period is from 40 hours of the original operation period to 110 hours at present, the efficiency and the yield are improved, and the internal quality is improved.)

1. A preparation method of PVDC preservative film is characterized by comprising the following steps:

(1) polyvinylidene chloride resin enters the screw groove and the screw cylinder through the feed opening and is melted at a high temperature of 170 ℃ to form molten resin;

(2) extruding a molten resin through a die head to form a cylindrical shape, putting the cylindrical molten resin into cooling water stored in a cooling tank, cooling the molten resin to form a parison, and injecting the cooling water and an opening agent into the parison;

(3) the parison cooled by cooling water is extruded by a first pinch roll to form a flat shape, the flat parison passing through the first pinch roll is continuously cooled when being in cooling water, is pulled out from the cooling water and then enters warm water at the temperature of 20 ℃ for curing, and then is sent out by a second pinch roll to enter a stretching device;

(4) the flat parison passing through the second pinch roll is stretched in the width direction by the internal pressure of air by introducing air into the flat parison in a stretching device, is extruded by upper and lower chevron plates to have a transverse width, enters a third pinch roll, is stretched by the difference in the rotation speed between the second pinch roll and the third pinch roll to form a cylindrical film, is formed into a flat shape by the third pinch roll, and is collected by a take-up device.

2. The method for preparing PVDC preservative film according to claim 1, wherein the method comprises the following steps: the clearance between the screw groove and the screw cylinder in the step (1) is controlled to be 3.8-4.2 mm, the extrusion capacity is controlled to be 60-80 kg/h, the length-diameter ratio of the screw is 1:18, and the feeding compression ratio is 1: 3.5.

3. The method for preparing PVDC preservative film according to claim 1, wherein the method comprises the following steps: and (4) the rotating speed of the third pinch roll is 3.9-4.3 times of that of the second pinch roll.

4. The method for preparing PVDC preservative film according to claim 1, wherein the method comprises the following steps: the stretching temperature of the parison in the step (4) is 20-40 ℃.

5. The method for preparing PVDC preservative film according to claim 1, wherein the method comprises the following steps: the preparation method of the opening agent in the step (2) comprises the following steps: taking 0.2kg of hot water at 100 ℃, adding 0.2kg of hydroxypropyl methylcellulose into the hot water, continuously stirring until the mixture becomes pasty, then adding 9.8kg of warm water, and continuously stirring during the stirring to ensure that the mixture is completely and uniformly fused.

6. The method for preparing PVDC preservative film according to claim 1 or 5, wherein the opening agent is 0.3 ~ 0.5.5 mL/kg of the polyvinylidene chloride resin.

7. The method for preparing PVDC preservative film according to claim 1, wherein the method comprises the following steps: the winding speed of the winding device is 39 meters/minute.

8. The method for preparing PVDC preservative film according to claim 1, wherein the method comprises the following steps: the herringbone plate is made of light aluminum alloy materials.

Technical Field

The invention belongs to the technical field of preservative film preparation, and particularly relates to a preparation method of a PVDC preservative film.

Background

The polyvinylidene chloride resin is sensitive to temperature in the processing process, equipment heating and rotational shearing heat can affect the polyvinylidene chloride melting state in the processing process, the matching between the screw groove and the screw barrel is particularly important, the gap size between the screw groove and the screw barrel and the screw operating state can affect the production quality of the preservative film, the quality of the preservative film in the prior art is unstable, and the quality problems of carbonization points, thin points and the like of the preservative film exist.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a preparation method of a PVDC preservative film, which solves the quality problems of carbonization points, thin points and the like of the preservative film in the prior art.

In order to solve the technical problems, the invention adopts the following technical scheme:

a preparation method of a PVDC preservative film comprises the following steps:

(1) polyvinylidene chloride resin enters the screw groove and the screw cylinder through the feed opening and is melted at a high temperature of 170 ℃ to form molten resin;

(2) extruding a molten resin through a die head to form a cylindrical shape, putting the cylindrical molten resin into cooling water stored in a cooling tank, cooling the molten resin to form a parison, and injecting the cooling water and an opening agent into the parison;

(3) the parison cooled by cooling water is extruded by a first pinch roll to form a flat shape, the flat parison passing through the first pinch roll is continuously cooled when being in cooling water, is pulled out from the cooling water and then enters warm water at the temperature of 20 ℃ for curing, and then is sent out by a second pinch roll to enter a stretching device;

(4) the flat parison passing through the second pinch roll is stretched in the width direction by the internal pressure of air by introducing air into the flat parison in a stretching device, is extruded by upper and lower chevron plates to have a transverse width, enters a third pinch roll, is stretched by the difference in the rotation speed between the second pinch roll and the third pinch roll to form a cylindrical film, is formed into a flat shape by the third pinch roll, and is collected by a take-up device.

Further, the clearance between the screw groove and the screw cylinder in the step (1) is controlled to be 3.8-4.2 mm, the extrusion capacity is controlled to be 60-80 kg/h, the length-diameter ratio of the screw is 1:18, feed compression ratio 1: 3.5.

further, the rotating speed of the third pinch roll in the step (4) is 3.9-4.3 times of that of the second pinch roll.

Further, the stretching temperature of the parison in the step (4) is 20 to 40 ℃, preferably 25 to 30 ℃.

Further, the preparation method of the opening agent in the step (2) is as follows: taking 0.2kg of hot water at 100 ℃, adding 0.2kg of hydroxypropyl methylcellulose into the hot water, continuously stirring until the mixture becomes pasty, then adding 9.8kg of warm water, and continuously stirring during the stirring to ensure that the mixture is completely and uniformly fused.

Further, the polyvinylidene chloride resin needs 0.3-0.5mL of the opening agent per kilogram.

Further, the winding speed of the winding device is 39 meters/minute.

Further, the herringbone plate is made of light aluminum alloy materials.

The invention has the beneficial effects that: the invention develops the screw with low productivity, the clearance between the screw groove and the screw barrel is controlled to be 3.8-4.2 mm, the extrusion amount can be controlled to be 60-80 kg per hour, the winding speed is 39 m/min, the winding is neat, the width is controllable, the carbonization point is reduced, and the operation period can reach 110 h. The original herringbone plate material is changed, the light aluminum alloy material is used, the opening angle of the herringbone plate can be increased, the maximum opening degree can reach 15cm, the friction force between the film bubble and the guide roller in the production process can be reduced, the resistance is smaller, and the bubble breaking problem in the production process is effectively improved. The chelating opening agent is used, the hydroxypropyl methylcellulose serving as the main component can be dissolved with water to form uniform solution, the concentration ratio of the uniform solution in the aqueous solution is 2%, the adhesive force of the opening agent can be improved, the adding frequency in the production process is reduced, the adhesive failure in the slitting process can be effectively reduced, the process waste is reduced, and the resource utilization rate is improved.

According to the preparation method of the preservative film, the screw rod is improved, the screw rod with low production capacity is used, the extrusion amount can be controlled to be 60 kg-80 kg per hour, the gap between the screw groove and the screw cylinder is adjusted to be 3.8-4.2 mm, the melting state of polyvinylidene chloride is more effectively controlled, and the quality problems of carbonization points, thin points and the like of the preservative film can be effectively solved. The original herringbone plate is made of resin materials, the gravity is large, the friction resistance is high, the maximum opening degree can only reach 4cm, and 52.5kg of bubbles are broken per ton, the novel herringbone plate is made of aluminum alloy light materials, the weight is small, the resistance is small, the maximum opening degree can reach 15cm, and 40.6kg of bubbles are broken per ton. The length-diameter ratio of the screw is 1:18, feed compression ratio 1:3.5, the continuous operation period is from 40 hours of the original operation period to 110 hours at present, the efficiency and the yield are improved, and the internal quality is improved: 53kg of carbon is cut per ton and reduced to 21 kg. Because most of the resin raw materials used by the preservative film are extracted from petroleum, the utilization rate of natural resources can be improved by 15 percent by using the production of the patent. The preservative film can be used for stabilizing a closed state, effectively improving the sealing property of packaging and prolonging the preservation time.

Detailed Description

The present invention will be further described with reference to the following examples. It is to be understood that the following examples are illustrative only and are not intended to limit the scope of the invention, which is to be given numerous insubstantial modifications and adaptations by those skilled in the art based on the teachings set forth above.