CN102304260A - Polyvinyl alcohol foaming material and manufacture method thereof - Google Patents

Abstract

The invention provides a polyvinyl alcohol foaming material and a manufacturing method thereof. The polyvinyl alcohol foaming material is prepared from a composition comprising the following components: 48-95 parts by weight of polyvinyl alcohol powder, preferably 67-95 parts by weight 5-40 parts by weight of plasticizer, preferably 5-25 parts by weight; 0.05-5 parts by weight of nucleating agent, preferably 0.1-3 parts by weight; 0.1-2 parts by weight of heat stabilizer, preferably 0.2-0.8 parts by weight; 0.02 to 5 parts by weight of a crosslinking agent, preferably 0.02 to 4 parts by weight; and a chemical foaming agent or a physical foaming agent. The manufacturing method can be a chemical foaming method or a physical foaming method. The chemical foaming method of the present invention has a simple process and is not demanding on equipment, and only needs an ordinary single-screw extruder for foaming; the physical foaming method of the present invention can also use the same foaming equipment without environmental Pollution is the foaming method that is currently highly recommended.

Description

A kind of polyvinyl alcohol foam material and its manufacturing method

technical field

The invention relates to a polyvinyl alcohol foam material and a manufacturing method thereof.

Background technique

Foamed polymer materials have been widely used in recent years, but the foamed materials currently on the market are poorly degradable and cause damage to the environment. Therefore, it is very difficult to produce a degradable foamed material to replace traditional polyolefin foamed materials. Is necessary.

Polyvinyl alcohol (PVA) is an environmentally friendly material. It contains a large number of hydroxyl groups in its molecular chain. It has the characteristics of hydrolytic degradation and biodegradation. It is not easy to burn, and the combustion products are water and carbon dioxide, so it does not pollute the environment. Polyvinyl alcohol products have good resistance to organic solvents, barrier properties and mechanical properties. Therefore, replacing common polyolefin foam materials with polyvinyl alcohol is of great significance for alleviating environmental pollution and reducing white pollution.

Due to the structural characteristics of polyvinyl alcohol, the melting temperature and decomposition temperature are close to the thermoplastic processing, and its foamed products are generally prepared by solution foaming method or molded foaming method. For example, in the patent application number 201010533209.6, polyvinyl alcohol, foaming aids, crosslinking agents, and catalysts are crosslinked and cured, and foamed in the early or middle stages of the crosslinking and curing process to form porous foam, and then further crosslinked and matured to obtain Sponge matrix. In the patent with the publication number CN1289629, the screened ultrafine starch particles are used as the cell nucleating agent, and after the polyvinyl alcohol sol is solidified and formed, the starch is washed away to obtain a fine-pored polyvinyl formal sponge.

In recent years, the melt processing of polyvinyl alcohol has been solved, and the extrusion foaming technology has low cost and high efficiency, and has received great attention. Publication number is that the patent of CN101153089 adopts water as foaming agent and plasticizer, foams through swelling, melt processing.

Contents of the invention

The object of the present invention is to provide a biodegradable polyvinyl alcohol foaming material with simple production method, low cost, high mechanical strength and a simple and feasible preparation method.

The inventors of the present invention have found through extensive research that only adding polyvinyl alcohol and a nucleating agent cannot produce a PVA foam material with uniform cell size distribution and good mechanical properties, which is directly related to the melt strength of polyvinyl alcohol. At low melt strength, due to the excessive gas pressure in the bubbles, polyvinyl alcohol cannot retain the gas, and the bubble walls are easy to break, and the generated cells mostly exist in the form of interconnection and merger. At high melt strength, due to excessive melt strength , the growth of bubbles is difficult, but because the bubbles cannot escape in the PVA matrix, only cells with larger cell sizes can be generated, or the generated cells are too large to merge, resulting in low foaming ratio and low foaming effect. not ideal. After polyvinyl alcohol is combined with plasticizers, nucleating agents, heat stabilizers and crosslinking agents, the melt strength of the polyvinyl alcohol matrix can be controlled, and foaming material formulations suitable for various foaming methods and foaming agents can be obtained .

The invention provides a polyvinyl alcohol foaming material, which is prepared from a composition comprising the following components: 48-95 parts by weight of polyvinyl alcohol powder, preferably 67-95 parts by weight; 5-40 parts by weight of plasticizer parts by weight, preferably 5 to 25 parts by weight; 0.05 to 5 parts by weight of nucleating agent, preferably 0.1 to 3 parts by weight; 0.1 to 2 parts by weight of heat stabilizer, preferably 0.2 to 0.8 parts by weight; 0.02 to 5 parts by weight of crosslinking agent, Preferably 0.02 to 4 parts by weight; and a chemical blowing agent or a physical blowing agent.

According to the polyvinyl alcohol foam material provided by the present invention, the degree of polymerization of the polyvinyl alcohol may be 500-2500, preferably 1700-2000. The degree of alcoholysis of polyvinyl alcohol in the present invention can be 74～99%, and the specific degree of alcoholysis can be determined according to the performance of the finished product: for samples that need low temperature water solubility, the preferred degree of alcoholysis is 74～88%, for low temperature It is not water-soluble, and requires high-temperature water-soluble and good barrier properties. The preferred alcoholysis degree is 89-99%. In addition, two or more polyvinyl alcohols can be doped to obtain proper properties. The higher the molecular weight, the greater the viscosity of the melt, the easier it is to degrade at high temperature, and the more difficult it is to melt process. Therefore, the present invention adopts different amounts and different types of heat stabilizers and auxiliary processing aids according to different polyvinyl alcohol molecular weights and degrees of alcoholysis. For example, polyvinyl alcohol with a degree of alcoholysis of 88% will release acetic acid gas when degraded, so it is necessary to assist an acid absorbent. Polyvinyl alcohol with a high degree of alcoholysis will degrade seriously due to the strong intermolecular force, so it is necessary to add Lubricant to increase the fluidity of polyvinyl alcohol with high degree of alcoholysis and reduce its degradation, the specific implementation will be reflected in the examples.

The polyvinyl alcohol powder as raw material of the present invention can be various commercially available PVA raw materials, for example can be the PVA series product of Japan Kuraray, Gohsenol (from Nippon Gonhsei), Poval (from Kuraray), Celvol (from Celanese) and CCP (from Changchun Petrochemical), preferably PVA117 (degree of alcoholysis 99%, degree of polymerization 1700), PVA217 (degree of alcoholysis 88%, degree of polymerization 1700) and PVA2088 (degree of alcoholysis 88%, degree of polymerization) of Japan Kuraray 2000).

According to the polyvinyl alcohol foam material provided by the present invention, wherein the plasticizer is one or more of the following, including ethylene glycol, polyethylene glycol, glycerin, pentaerythritol, caprolactam, propylene glycol, trihydroxy One or more of methylpropane, pentylene glycol, sorbitol, ethanolamine, diethanolamine, acetamide, dimethylformamide and ethylenediamine, preferably ethylene glycol, glycerol, pentaerythritol, caprolactam and One or more of diethanolamine.

Table 1 lists the plasticization data of high degree of alcoholysis PVA117, among them. As can be seen from Table 1, after adding the plasticizer, the melting point of the plasticized PVA is lower than that of pure PVA, which shows that the compound plasticizer of the present invention significantly reduces the melting point of PVA after adding the plasticizer, making the processing window T _f -T _m increases (T _f is the decomposition temperature, T _m is the melting point), so that PVA has the performance of thermoplastic processing, and the crystallization temperature (T _p ) and crystallinity (X _c ) are also lower than pure PVA, indicating that The addition of plasticizer weakens the hydrogen bond between PVA molecules and intramolecules, and the formation of new hydrogen bonds between the plasticizer and PVA leads to a decrease in the regularity of PVA. Since the plasticizer enters the PVA molecular chain, it will The plasticizer needs to migrate out of the PVA molecular chain to complete the crystallization, so the crystallization behavior is delayed and the crystallinity is reduced. The plasticizer of the invention can realize the melt processing of PVA with high degree of alcoholysis.

Table 1

The nucleating agent can be an inorganic nucleating agent such as talcum powder, calcium carbonate, nano-montmorillonite, nano-clay, nano-silica, mica, preferably, the particle size of the inorganic nucleating agent can be 200-3000 Mesh, preferably 1000-3000 mesh, moisture content ≤ 0.5%, can also be an organic nucleating agent, such as carboxylic acid and its metal salts, sorbitol, aryl phosphate, rosin acid soap, or polymer composition The nucleating agent is one or more of polyethylene glycol with a molecular weight of 400-1000, and HEC (PVA0588). The particle size and dosage of the nucleating agent can be determined according to the needs of different cells.

The heat stabilizer may be a conventional heat stabilizer in the art. For example, it may be one or more of a radical absorber, a radical stabilizer, a lubricant, and an active substance absorber. In a preferred embodiment, the free radical absorbent may include a primary absorbent and an auxiliary absorbent, and the primary absorbent may include an alkylphenol compound, an alkylene phenol compound, an alkyl bisphenol compound, Hydroxyphenyl acrylate compounds, aminophenol compounds, thiobisphenol compounds or combinations thereof. Absorption aids include hydroxy ester compounds, saturated ester compounds, thioester compounds, phosphite compounds or combinations thereof. The free radical stabilizer may include organic salts formed of metals such as Ca, Ba, Sn, organic ester salts formed of Zn or Cd, diketone compounds, organic metal salts or combinations thereof. The lubricant may include hydrocarbon lubricants such as solid paraffin, liquid paraffin, fatty acids such as stearic acid, ricinoleic acid, aliphatic amides and esters such as stearamide, butyl stearate, stearic acid Glycerides, and metal soaps, such as one or more of zinc stearate, barium stearate, and calcium stearate. The active substance absorbent may include inorganic bases, inorganic salts, combinations of inorganic bases and inorganic salts, combinations of inorganic bases and/or inorganic salts and polymethylol compounds, and combinations of the above substances or combinations with nano-compounds. Preferably, the heat stabilizer used in the present invention can be an alkylphenol compound, an alkylene phenol compound, an alkyl bisphenol compound, a hydroxyphenyl acrylate compound, an aminophenol compound, a thiobisphenol Compounds, hydroxy ester compounds, saturated ester compounds, thioester compounds, phosphite compounds, alkyl tin thioglycolate, butyl tin thiol propionate, octyl tin thiol acetate, One or more of barium stearate, calcium stearate, zinc stearate, dibasic lead phosphite, dibasic lead stearate, tribasic lead sulfate, and 1,3-diketone compounds species, preferably one or more of alkylphenol compounds, thiobisphenol compounds, thioester compounds, phosphite compounds, barium stearate and calcium stearate. Specifically, the heat stabilizer used in the present invention may preferably be the heat stabilizer described in the patent application with application number 200810180879.7, which is incorporated herein by reference in its entirety.

The crosslinking agent can be organic silanes, such as vinyl silane, epoxy silane, amino silane, too esters such as monoalkyl titanate, monoalkoxy phosphate titanate, organic Chromium, titanium (TiO ₂ ), and silicon, such as one or more of nano-silica, organic dibasic acid and polyhydric alcohol, preferably nano-silica or polyhydric alcohol.

Described chemical blowing agent can be any chemical blowing agent known in the art, for example, can be azodicarbonamide blowing agent, sodium bicarbonate, azobisisobutyronitrile, hydrazide, methylenetetramine One or more of them are preferably azodicarbonamide blowing agent or sodium bicarbonate. The consumption of described chemical foaming agent can be easily determined by those skilled in the art according to the degree of foaming required, generally speaking, with the polyvinyl alcohol of 100 weight parts as a benchmark, the consumption of chemical foaming agent can be 0.08～ 5 parts by weight, preferably 0.2 to 2 parts by weight. Described physical blowing agent can be any physical blowing agent known in the art, for example, can be supercritical gas, preferably one or more in supercritical nitrogen, supercritical carbon dioxide and supercritical butane, preferably supercritical nitrogen. Based on 100 kg of polyvinyl alcohol, the amount of supercritical gas can be 0.5-5 liters, preferably 1-3 liters.

The present invention also provides the method A (chemical foaming method) of making above-mentioned polyvinyl alcohol foaming material, and this method comprises the steps:

(1) polyvinyl alcohol powder is blended with plasticizer in mixer;

(2) extruding and pelletizing the blend obtained in step (1) with a twin-screw extruder to obtain pellets;

(3) mixing the pellets obtained in step (2) with the processing aid in a mixer to obtain a uniform mixture;

(4) Adding a chemical foaming agent to the mixed material obtained in step (3), after mixing evenly, extrude with a single-screw extruder or multiple single-screw extruders connected in series to obtain a polyvinyl alcohol foamed product;

Wherein, optionally, the above-mentioned steps (2), (3) are the following steps (2'): mix the mixed material obtained in the step (1) with a processing aid and a chemical foaming agent in a mixer to obtain a uniform and the above-mentioned step (4) is the following step (3'): the mixed material obtained in step (2') is extruded with a single-screw extruder or multiple single-screw extruders connected in series to obtain polyethylene Alcohol foaming products.

In above-mentioned method A (that is, chemical foaming method), the method that carries out according to step (1) (2) (3) (4) can be called chemical blowing agent two-step foaming method; According to step (1) The method carried out in (2')(3') can be called a one-step foaming method of continuous extrusion of a chemical blowing agent.

The present invention also provides another kind of method B (physical foaming method) of making above-mentioned polyvinyl alcohol foaming material, and this method comprises the steps:

(a) polyvinyl alcohol powder is blended with plasticizer in mixer;

(b) extruding and pelletizing the blend obtained in step (a) with a twin-screw extruder to obtain pellets;

(c) mixing the pellets obtained in step (b) with processing aids (nucleating agent, crosslinking agent, heat stabilizer) in a mixer to obtain a uniform mixture;

(d) Extrude the mixture obtained in step (c) with a single-screw extruder or multiple single-screw extruders connected in series, and inject supercritical gas into the polyvinyl alcohol melt during the extrusion process to obtain polyvinyl alcohol Vinyl alcohol foam products;

Wherein, alternatively, the above steps (b), (c) are the following steps (b'): the blend obtained in step (a) and processing aids (nucleating agent, crosslinking agent, heat stabilizer ) mixing in a mixer to obtain a homogeneous mixture; and the above step (d) is the following step (c'): the mixture obtained in step (b') is used with a single screw extruder or a plurality of single-screw extruders connected in series Extruded by a screw extruder, during which supercritical gas is injected into the polyvinyl alcohol melt to obtain polyvinyl alcohol foamed products.

In the above-mentioned method B (that is, physical foaming method), the method carried out according to steps (a) (b) (c) (d) can be referred to as a physical blowing agent two-step foaming method; according to step (a) The method performed by (b') (c') can be called a physical blowing agent continuous extrusion one-step foaming method.

According to the production method provided by the present invention, wherein, in steps (1) and (a), the blending temperature can be 30-150°C, preferably 50-130°C, and the blending time can be 10-60min, preferably 20-50 minutes.

The twin-screw extruder in the steps (2) and (b) can preferably be a twin-screw extruder with an aspect ratio of 28-32:1 and a diameter of 30-65 mm, preferably a parallel co-rotating twin-screw extruder , the extrusion conditions include: the temperature may be 150-250° C., preferably 170-240° C.; the rotation speed may be 30-200 revolutions/second, preferably 50-150 revolutions/second. Preferably, the pellets obtained from steps (2) and (b) have a particle diameter of 0.1-0.8 mm. For example, in a preferred embodiment, under slight vibration, about 95% of the total weight of 20 kg of pellets can pass through a 25-mesh sieve within 5 minutes, and about 99% of the total weight can pass through a 20-mesh sieve.

According to the manufacturing method provided by the present invention, the mixing temperature in steps (3) and (c) may be 20-40° C., and the mixing time may be 5-30 minutes.

According to the manufacturing method of the present invention, methods A and B are implementations of chemical foaming and physical foaming, respectively. Wherein, the aspect ratio of the single-screw extruder in the steps (4), (d), (3') and (c') can be 28-60:1, and the diameter can be 30-65mm, extruding The conditions include: the temperature can be 150-250° C., preferably 170-240° C.; the rotation speed can be 5-150 revolutions/second, preferably 10-100 revolutions/second.

According to the production method of the present invention, in steps (2') and (b'), the mixing temperature can be 5-80°C, preferably 20-60°C, and the blending time can be 10-50min, preferably 20min. ~40min.

In the chemical foaming method, the chemical foaming agent can be any chemical foaming agent known in the art, for example, it can be azodicarbonamide foaming agent, sodium bicarbonate, azobisisobutyronitrile, acyl One or more of hydrazine and methylenetetramine, preferably azodicarbonamide blowing agent or sodium bicarbonate. The consumption of described chemical foaming agent can be easily determined by those skilled in the art according to the degree of foaming required, generally speaking, with the polyvinyl alcohol of 100 weight parts as a benchmark, the consumption of chemical foaming agent can be 0.08～ 5 parts by weight, preferably 0.2 to 2 parts by weight. In the physical foaming method, the physical foaming agent used is a supercritical gas, which can be one or more of supercritical nitrogen, supercritical carbon dioxide and supercritical butane, preferably supercritical nitrogen.

The chemical foaming method of the present invention has a simple process and is not demanding on equipment, and only needs an ordinary single-screw extruder for foaming; the physical foaming method of the present invention can also use the same foaming equipment without environmental Pollution is the foaming method that is currently highly recommended.

The main difference between the present invention and the prior art (such as the patent of publication number CN101153089) is that the foaming agent used in the present invention is not water, and in the foaming process, polyvinyl alcohol can be plasticized by a plasticizer to obtain polyvinyl alcohol. Vinyl alcohol pellets, and then the polyvinyl alcohol pellets, foaming agent, processing aids, etc. are continuously extruded and foamed on a single-screw extruder, and plasticizers, foaming agents, processing aids, etc. can also be mixed together Continuous extrusion and foaming in a twin-screw extruder, or foaming by supercritical gas foaming. The prepared polyvinyl alcohol foaming material can be used for filtering and absorbing materials for water treatment, sound-insulating and heat-insulating materials, soil moisturizing, fresh-keeping and multifunctional composite foam materials.

Description of drawings

Below, describe embodiment of the present invention in detail in conjunction with accompanying drawing, wherein:

Fig. 1 is the scanning electron micrograph of the polyvinyl alcohol foam material that the embodiment of the present invention 1 makes;

Fig. 2 is the scanning electron micrograph of the polyvinyl alcohol foam material that the embodiment of the present invention 2 makes;

Fig. 3 is the scanning electron micrograph of the polyvinyl alcohol foam material that the embodiment of the present invention 3 makes;

Fig. 4A-B is the schematic flow sheet of chemical foaming method of the present invention, wherein Fig. 4A is chemical foaming agent two-step foaming method; Fig. 4B is chemical foaming agent continuous extrusion one-step foaming method;

Figure 5A-B is a schematic flow sheet of the physical foaming method of the present invention, wherein Figure 5A is a two-step foaming method of a physical foaming agent; Figure 5B is a continuous extrusion one-step foaming method of a physical foaming agent;

Fig. 6 is the scanning electron micrograph of the polyvinyl alcohol foam material that comparative example 1 makes;

Fig. 7 is the scanning electron micrograph of the polyvinyl alcohol foam material that comparative example 2 makes;

FIG. 8 is a scanning electron micrograph of the polyvinyl alcohol foam material prepared in Comparative Example 3.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, and the given examples are only for clarifying the present invention, not for limiting the scope of the present invention.

Example 1

The present embodiment prepares the foamed material by the chemical foaming method according to the manufacturing method of the present invention

Raw materials used in this embodiment:

Polyvinyl alcohol powder (Japan Kuraray, PVA217) 100kg;

Caprolactam (plasticizer) 10kg;

Ethylene glycol (plasticizer) 15kg

Talc powder (nucleating agent) 0.5kg;

Silica (crosslinking agent) 3kg;

Octyltin T890 (heat stabilizer, Guangzhou Denghua Chemical Co., Ltd.) 0.5kg;

DSTP (phosphite antioxidant, Beijing Institute of Auxiliaries) 0.2Kg

Azodicarbonamide (chemical foaming agent, Henan Jintai Chemical Industry) 0.5kg;

Magnesium hydroxide (acid absorbent) 0.2kg.

Prepare foam material with above-mentioned raw material:

(1) Blend polyvinyl alcohol powder with caprolactam, ethylene glycol, antioxidant 1098 and DSTP in a high-speed mixer, keep the temperature below 100°C during the mixing process, and mix the above compounds for a uniform time So far, the mixture is powder when it is discharged;

(2) The blend obtained in step (1) is extruded with a twin-screw extruder and pelletized to obtain pellets with a particle size of 0.5 mm, wherein the aspect ratio of the twin-screw extruder is 30:1 , the diameter is 50mm, the rotating speed is 50rpm, and the temperature of each zone is shown in Table 2:

Table 2

section Feeding area Zone 2 Zone 3 Zone 4 District 5 machine head Temperature/℃ 160 180 210 210 190 185

(3) Mix the pellets prepared in step (2) with crosslinking agent, nucleating agent, and foaming agent in a high-speed mixer. During the mixing process, the temperature is always kept below 30°C, and the mixing time is about 5 minutes to obtain a mixture material;

(4) extruding the mixture obtained in step (3) through a single-screw extruder to obtain a polyvinyl alcohol foaming material, wherein the aspect ratio of the single-screw extruder is 40:1, the diameter is 30 mm, and the rotating speed 30rpm, the temperature of each zone is shown in Table 3:

table 3

section Feeding area Zone 2 Zone 3 Zone 4 District 5 machine head Temperature/℃ 165 190 220 220 190 180

According to the national standard GB/T6343-1995, the density test was carried out by a density tester (ULTRAPYC 1200e, Quantachrome Instruments), and the tensile strength and elongation at break were measured according to the national standard GB/T 6344-1996. The scanning electron micrograph of the foam material obtained in this embodiment is shown in Figure 1. As can be seen from Figure 1, the obtained PVA foam material has uniform cell distribution, uniform wall thickness, no cell merging phenomenon, and cell size About 250um. The foamed material prepared by the present invention has a tensile strength of 13.6 MPa, an elongation at break of 183.8%, and an apparent density of 0.42 g/cc.

Example 2

Present embodiment prepares foamed material with physical foaming method according to manufacturing method of the present invention

Raw material used in this embodiment:

Polyvinyl alcohol powder (Kuraray, Japan, PVA117) 100kg;

Pentaerythritol (plasticizer) 15kg;

Trimethylolpropane (plasticizer) 8kg;

Calcium carbonate (nucleating agent, Qingdao Boxin Chemical Co., Ltd. 2000 mesh) 0.15kg;

Nanoclay (nucleating agent) 0.22kg;

Calcium stearate (lubricant) 0.3kg;

Hindered phenolic antioxidant 1076 (Beijing Auxiliary Research Institute) 0.10kg

Phosphite heat stabilizer (Beijing Auxiliary Research Institute) 0.3kg;

(1) Blend polyvinyl alcohol powder with pentaerythritol, heat stabilizer and trimethylolpropane in a high-speed mixer, keep the blending temperature below 49°C, and blend for 50 minutes. When the mixture is discharged in powder form;

(2) The blend obtained in step (1) is extruded with a twin-screw extruder and pelletized to obtain pellets with a particle size of 0.8 mm, wherein the aspect ratio of the twin-screw extruder is 32:1 , the diameter is 40mm, the rotational speed is 140rpm, and the temperature of each zone is shown in Table 4:

Table 4

section Feeding area Zone 2 Zone 3 Zone 4 District 5 machine head Temperature/℃ 160 180 210 210 210 208

(3) Mix the granules prepared in step (2) with a crosslinking agent and a nucleating agent in a high-speed mixer. During the mixing process, the temperature is 25° C., and the mixture is mixed for about 10 minutes to obtain a mixed material;

(4) the mixed material obtained by step (3) is extruded by a single-screw extruder, and supercritical N is injected into the polyvinyl alcohol melt in the _2nd district by a supercritical gas injection system (system pressure is 12MPa, injection rate It is 2 liters), make supercritical N exist in liquid form in the screw rod, through the shearing and mixing of the screw rod, the liquid and the polyvinyl alcohol melt are fully mixed evenly, through the die, _pressure relief, extrusion, cooling and molding, to obtain Polyvinyl alcohol foaming material, wherein, the length-to-diameter ratio of the single-screw extruder is 55:1, the diameter is 60 mm, the rotating speed adopts 10, 15, 20, 30, 40 and 80 rpm respectively, and the temperatures in each zone are shown in Table 5 :

table 5

section Feeding area Zone 2 Zone 3 Zone 4 District 5 machine head Temperature/℃ 180 230 230 225 220 205

The scanning electron micrographs of the foamed material prepared under different rotating speeds in the present embodiment are as shown in Figure 2, wherein a, b, c, d, e and f are successively adopted 10, 15, 20, 30, 40 and 80rpm The electron microscope image of the foamed material obtained by the rotating speed, comparing a, b, c, d, e and f, it can be seen that at a low shear rate, the cell density is relatively large and the cell distribution is uniform. Cell distribution and size are not uniform. As the rotational speed increases, the viscosity of the PVA melt decreases, so the cell merging phenomenon in Figure b appears, and the bubbles appear as deformed round or oval, and some cells do not have complete cell walls, and there are more Hollow, opening ratio increases, foaming ratio of foaming material decreases, foam density increases, the relationship between apparent density and screw speed is shown in Table 6, the mechanical test results of foaming materials show that the mechanical properties of foaming materials are related to the material The cell density of the material has a great relationship. The tensile strength and elongation at break of the material with uniform cell distribution and complete cell shape are higher. If the material cells are seriously merged or the cell distribution is uneven, the material's The mechanical properties are poor.

Table 6

Screw speed(rpm) 10 15 20 30 40 80 Density (g/cc) 0.46 0.54 0.59 0.67 0.83 0.87

Example 3

The present embodiment prepares the foamed material by the chemical foaming method according to the manufacturing method of the present invention

Raw materials used in this embodiment:

Polyvinyl alcohol powder (Kuraray, Japan, PVA2088) 100kg;

Glycerol (plasticizer) 5kg;

Pentylene glycol (plasticizer) 5kg

Polyethylene glycol 400 (nucleating agent, Sinopharm Chemical Reagent Co., Ltd.) 0.5kg;

Mica (nucleating agent) 0.22kg;

Zinc stearate (lubricant) 0.3kg;

AO31 (Beijing Auxiliary Research Institute) 0.1Kg;

AO-5 (Beijing Auxiliary Research Institute) 0.2Kg;

Phosphite heat stabilizer (Beijing Auxiliary Research Institute) 0.4kg;

Sodium bicarbonate (acid absorbent) 2kg;

Azobisisobutyronitrile (chemical foaming agent) 0.3kg.

(1) In a high-speed mixer, polyvinyl alcohol powder is mixed with glycerol, pentanediol, heat stabilizer, crosslinking agent, nucleating agent and chemical foaming agent sodium bicarbonate, azobisisobutyronitrile Blending, the blending temperature is 49°C, and the blending time is 50min;

(2) The blend obtained in step (1) is directly extruded and foamed with a twin-screw extruder, wherein the aspect ratio of the twin-screw extruder is 32:1, the diameter is 40 mm, and the rotation speed is 140 rpm. The temperature is shown in Table 7:

Table 7

section Feeding area Zone 2 Zone 3 Zone 4 District 5 machine head Temperature/℃ 160 180 200 220 220 220

Fig. 3 is the SEM picture of the foamed material of the embodiment, as can be seen from the figure, the cell size is about 200um, the cells are uniform, and the blast hole wall is relatively thin.

Measure according to the method identical with embodiment 1, the tensile strength of the foamed material that present embodiment makes reaches 15.6Mpa, and elongation at break is 163.8%, and apparent density is 0.35g/cc, and expansion ratio is 3.8 times.

Comparative example 1

Foaming material is prepared according to the manufacturing method in CN101153089

Add 2kg of polyoxyethylene and 2kg of glutaraldehyde into 15kg of deionized water and stir evenly, add 45kg of polyvinyl alcohol pellets with a degree of polymerization of 1700 and a degree of alcoholysis of 92mol.%. Fully swell. After fully swollen, add 2kg of calcium carbonate and 20kg of hydroxymethyl cellulose. After mixing evenly, melt and extrude foaming in an extruder at a temperature of 170°C to prepare a polyvinyl alcohol foam sheet.

Figure 6 is the SEM picture of the foamed material of this comparative example. It can be seen from the figure that the cell size of the foamed material is not uniform, the cell merger phenomenon is serious, and the cell wall is very thick, and the foaming process is not easy to control.

Comparative example 2

Foaming material is prepared according to the manufacturing method in CN101153089

Add 0.5kg of citric acid, 0.5kg of borax and 5kg of urea into 40kg of deionized water and stir evenly, add 50kg of polyvinyl alcohol pellets with a degree of polymerization of 900 and a degree of alcoholysis of 99mol.%. Fully swell in the container, after fully swollen, add 5kg of silicon dioxide, 4kg of ammonium oleate and 15kg of activated carbon, mix evenly, and prepare polyvinyl alcohol foamed beads in a hot press at a temperature of 140°C.

Fig. 7 is the SEM picture of the foamed material of this comparative example, it can be seen from the figure that the cell size distribution is wide, the cell size is large, and the cell merger phenomenon is serious.

Comparative example 3

Foaming material is prepared according to the manufacturing method in CN101153089

1kg epichlorohydrin, 4kg polyethylene glycol and 6kg acetamide are added to 15kg deionized water and stirred evenly, and 85kg of polyvinyl alcohol pellets with a degree of polymerization of 2400 and a degree of alcoholysis of 92mol.% are added, and stirred at temperature Fully swell in a closed container at 50°C, after fully swelling, add 2kg of talcum powder, 2kg of zinc stearate and 10kg of chitosan, mix well, and prepare polyvinyl alcohol foam in a hot press at 150°C film.

Figure 8 is the SEM picture of the foam material of this comparative example. It can be seen from the figure that the cells of the PVA foam material are unevenly distributed. Bubble ratio is small.

The tensile strength, elongation at break, apparent density and expansion ratio of the foamed materials obtained in Comparative Examples 1-3 were measured according to the same method as in Example 1, and the results are listed in Table 8.

Table 8

samples Comparative example 1 Comparative example 2 Comparative example 3 Tensile strength (MPa) 12.50 13.13 9.64 Elongation at break (%) 156.71 176.70 147.67 Apparent density (g/cc) 1.29 1.26 1.19 Foaming ratio 1.03 1.05 1.12

Comparing the data in Table 8 with the data of the samples of the examples of the present invention, it can be seen that the mechanical properties of the samples of the comparative examples are inferior to those of the PVA foamed products of the present invention, and the expansion ratio is also small.

Claims (15)

1. A polyvinyl alcohol foaming material, which is made from a composition comprising the following components: 48 to 95 parts by weight of polyvinyl alcohol powder, preferably 67 to 95 parts by weight; 5 to 40 parts by weight of plasticizer, Preferably 5-25 parts by weight; 0.05-5 parts by weight of nucleating agent, preferably 0.1-3 parts by weight; 0.1-2 parts by weight of heat stabilizer, preferably 0.2-0.8 parts by weight; 0.02-5 parts by weight of cross-linking agent, preferably 0.02 parts by weight - 4 parts by weight; and a chemical blowing agent or a physical blowing agent. 2. The polyvinyl alcohol foam material according to claim 1, wherein the degree of polymerization of the polyvinyl alcohol can be 500 to 2500, preferably 1700 to 2000; preferably, the degree of alcoholysis of the polyvinyl alcohol is 74-99%. 3. polyvinyl alcohol foam material according to claim 1 and 2, wherein, said plasticizer is ethylene glycol, polyethylene glycol, glycerol, pentaerythritol, caprolactam, propylene glycol, trimethylol propane , pentylene glycol, sorbitol, ethanolamine, diethanolamine, one or more of acetamide, dimethylformamide and ethylenediamine, preferably ethylene glycol, glycerol, pentaerythritol, caprolactam and diethanolamine one or more of . 4. The polyvinyl alcohol foam material according to any one of claims 1 to 3, wherein the nucleating agent is one or more of an inorganic nucleating agent or an organic nucleating agent, and the inorganic nucleating agent The nucleating agent is talcum powder, calcium carbonate, nano-montmorillonite, nano-clay, nano-silica and mica, preferably, the particle diameter of the inorganic nucleating agent is 200-3000 mesh, and the moisture content is ≤0.5%; The organic nucleating agent is carboxylic acid and its metal salt, sorbitol, aryl phosphate, rosin acid soap or macromolecular nucleating agent, and the macromolecular nucleating agent is such as polyethylene glycol, low polymerization degree One or more of PVA. 5. The polyvinyl alcohol foam material according to any one of claims 1 to 4, wherein the heat stabilizer is one of a free radical absorber, a free radical stabilizer, a lubricant and an active substance absorber one or more species. 6. The polyvinyl alcohol foam material according to any one of claims 1 to 5, wherein the crosslinking agent is organosilanes, such as vinyl silanes, epoxy silanes, amino silanes, titanic acid Esters, such as one or more of monoalkyl titanate and monoalkoxy phosphate titanate, organic chromium, titanium and silicon, organic dibasic acid and polyhydric alcohol, preferably Nano silica or polyol. 7. The polyvinyl alcohol foam material according to any one of claims 1 to 6, wherein the chemical blowing agent is azodicarbonamide blowing agent, sodium bicarbonate, azobisisobutyronitrile , hydrazide, one or more of methylenetetramine, preferably azodicarbonamide blowing agent or sodium bicarbonate; preferably, based on 100 parts by weight of polyvinyl alcohol, the chemical The consumption of foaming agent is 0.08～5 weight parts, more preferably 0.2～2 weight parts; Described physical foaming agent is supercritical gas, is preferably a kind of in supercritical nitrogen, supercritical carbon dioxide and supercritical butane or more, most preferably supercritical nitrogen; preferably, based on 100kg of polyvinyl alcohol, the amount of supercritical gas used is 0.5-5 liters, more preferably 1-3 liters. 8. a method for manufacturing the polyvinyl alcohol foam material described in any one of claims 1 to 7, the method may further comprise the steps: (1) polyvinyl alcohol powder is blended with plasticizer in mixer; (2) extruding and pelletizing the blend obtained in step (1) with a twin-screw extruder to obtain pellets; (3) mixing the pellets obtained in step (2) with a nucleating agent, a heat stabilizer and a crosslinking agent in a mixer to obtain a uniform mixture; (4) Adding a chemical foaming agent to the mixed material obtained in step (3), after mixing evenly, extrude with a single-screw extruder or multiple single-screw extruders connected in series to obtain a polyvinyl alcohol foamed product; Wherein, alternatively, the above-mentioned steps (2), (3) are the following steps (2'): the mixed material obtained in the step (1) is mixed with a nucleating agent, a heat stabilizer, a cross-linking agent and a chemical blowing agent Mix in a mixer to obtain a uniform mixed material; and the above-mentioned step (4) is the following step (3'): the mixed material obtained in the step (2') is extruded with a single-screw extruder or a plurality of single-screws connected in series The polyvinyl alcohol foamed product is extruded by an extruder. 9. a method for manufacturing the polyvinyl alcohol foam material described in any one of claims 1 to 7, the method may further comprise the steps: (a) polyvinyl alcohol powder is blended with plasticizer in mixer; (b) extruding and pelletizing the blend obtained in step (a) with a twin-screw extruder to obtain pellets; (c) mixing the pellets obtained in step (b) with a nucleating agent, a heat stabilizer and a crosslinking agent in a mixer to obtain a uniform mixture; (d) Extrude the mixture obtained in step (c) with a single-screw extruder or multiple single-screw extruders connected in series, and inject supercritical gas into the polyvinyl alcohol melt during the extrusion process to obtain polyvinyl alcohol Vinyl alcohol foam products; Wherein, alternatively, the above-mentioned steps (b), (c) are the following steps (b'): the blend obtained in step (a) is mixed with a nucleating agent, a thermal stabilizer and a crosslinking agent in a mixer Mix to obtain a uniform mixed material; and the above-mentioned step (d) is the following step (c'): the mixed material obtained in the step (b') is extruded with a single-screw extruder or a plurality of single-screw extruders connected in series In the extrusion process, supercritical gas is injected into the polyvinyl alcohol melt to obtain polyvinyl alcohol foamed products. 10. The method according to claim 8 or 9, wherein, in steps (1) and (a), the temperature of blending is 30 to 150° C., preferably 50 to 130° C., and the time of blending is 10 to 100° C. 60 minutes, preferably 20 to 50 minutes. 11. The method according to claim 8 or 9, wherein, the aspect ratio of the twin-screw extruder in the steps (2) and (b) is 28 to 32: 1, and the diameter is 30 to 65 mm. The selected conditions include: the temperature is 150-250° C., preferably 170-240° C.; the rotation speed is 30-200 rpm. 12. The method according to claim 8 or 9, wherein the pellets obtained from steps (2) and (b) have a particle diameter of 0.1-0.8 mm. 13. The method according to claim 8 or 9, wherein the mixing temperature in steps (3) and (c) is 20-40°C, and the mixing time is 5-30min. 14. The method according to claim 8 or 9, wherein the aspect ratio of the single-screw extruder described in steps (4), (d), (3') and (c') is 28～60: 1. The diameter is 30-65mm. The extrusion conditions include: temperature 150-250°C, preferably 170-240°C; rotation speed 5-150 rpm. 15. The method according to claim 8 or 9, wherein the mixing temperature in steps (2') and (b') is 5-80°C, preferably 20-60°C, and the mixing time is 10-50min, Preferably it is 20-40 minutes.

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