CN112391020B - PVA film for demolding and preparation method thereof - Google Patents
PVA film for demolding and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a PVA film for demolding and a preparation method thereof, wherein the PVA film for demolding comprises the following raw materials in percentage by weight: 60-80% of PVA, 10-30% of plasticizer, 0.2-1.0% of cross-linking agent, 0.1-1% of heat stabilizer, 2-10% of wet strength agent, 2-10% of water repellent agent and the balance of water. The PVA film for demolding has reasonable recipe and raised water resistance.
Description
Technical Field
The invention relates to the field of demolding films, and mainly relates to a PVA film for demolding and a preparation method thereof.
Background
Besides water solubility, polyvinyl alcohol (PVA) has the characteristics of good compactness, high crystallinity and strong bonding force, and a film prepared from the PVA not only has flexibility, smoothness and non-electrification property, but also has oil resistance, solvent resistance, wear resistance and good gas barrier property, and has wide application scenes in industry. The application fields are mainly two main types, packaging films and carrier films. The packaging film has more research at home and abroad, the research in the field of carrier films is less, and except for being used for embroidery substrate and water transfer printing, other products only have a few data reports and can be applied, and the packaging film is rarely used in industrial production. The PVA marble demoulding film is used as a carrier film, has the characteristics of good release and high temperature resistance with epoxy plastic resin, unsaturated plastic resin and other thermoplastic plastics, and can be more attached to a mould by adopting the high flexibility of PVA when parts are manufactured by adopting unsaturated polyester, epoxy resin or other hot resin agents, so that the demoulding quality is improved, the release is good, and impurities are not generated after demoulding. Although data are reported early, the method is a mature application in foreign countries, the technology is firmly held by manufacturers in the United states and Japan, a well-known manufacturer is Korea and domestic manufacturers are always in industrial production without finding a breakthrough. The method is mainly characterized in that the domestic manufacturer recognizes marble demoulding products to have a certain misunderstanding, thinks that the PVA film which is convenient can be used as the marble demoulding film products, and through communicating with the Korean marble manufacturers and using tests, compared with the cola products, finds that the products suitable for marble demoulding are high-temperature water-soluble products and need to have higher water resistance so as to ensure that the marble products do not generate swelling phenomenon due to reaction with water when contacting with high-temperature slurry, thereby generating ripples. The domestic high-temperature film is produced by adopting a solution casting mode, the crystallinity is low, and meanwhile, in order to ensure the plasticizing effect, a large amount of plasticizer and a small amount of cross-linking agent are added, and meanwhile, only PVA products with low alcoholysis degree (the alcoholysis degree is 98%) can be selected, so that the prepared film cannot keep non-swelling in hot water with the temperature of more than 40 ℃.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a PVA film for demolding and a preparation method thereof, and aims to solve the problem that the water resistance of the conventional PVA film for demolding cannot meet the requirement of marble demolding production and use.
The technical scheme of the invention is as follows:
a PVA film for demolding comprises the following raw materials in percentage by weight:
60-80% of PVA, 10-30% of plasticizer, 0.2-1.0% of cross-linking agent, 0.1-1% of heat stabilizer, 2-10% of wet strength agent, 2-10% of water repellent agent and the balance of water.
The PVA film for demolding is characterized in that PVA with alcoholysis degree of more than 99.5% is selected as PVA.
The PVA film for demolding is PVA powder with 80 mesh over.
The PVA film for demolding is characterized in that the plasticizer is a combination of a micromolecule plasticizer and a macromolecule plasticizer; the weight ratio of the small-molecule plasticizer to the large-molecule plasticizer is 0.5 to 1; the micromolecular plasticizer is a monomolecular substance, and the macromolecular plasticizer is a polymer with the polymerization degree of more than 400.
The PVA film for demolding is characterized in that the micromolecular plasticizer is glycerol, triethanolamine, propylene glycol, caprolactam or trimethylolpropane; the macromolecular plasticizer is polyethylene glycol, polypropylene glycol or polyglycerol.
The PVA film for mold release, wherein the heat stabilizer comprises sodium hydroxide.
The PVA film for demolding is characterized in that the heat stabilizer is sodium hydroxide and sodium oxalate, and the weight ratio of the sodium hydroxide to the sodium oxalate is 1-3.
The PVA film for demolding is characterized in that the cross-linking agent is boric acid, borax or an aqueous organic titanium cross-linking agent Tyzor371;
the wet strength agent is polyamide polyamine epichlorohydrin resin or polyamide epichlorohydrin resin;
the water repellent agent is self-crosslinking and self-drying resin; the self-crosslinking and self-drying resin is one or the combination of more than two of water-based acrylic acid, water-based epoxy resin, water-based urea-formaldehyde resin and water-soluble phenolic resin.
A method for preparing the PVA film for demoulding as described above comprises the following steps:
mixing PVA with a plasticizer, a cross-linking agent, a heat stabilizer, a wet strength agent, a water repellent agent and water, then carrying out extrusion granulation, sealing, storing and aging the granules for 30-60h, carrying out extrusion film blowing on the granules, and carrying out post-treatment shaping to obtain the PVA film for demolding with the thickness of 20-40 mu m.
The preparation method of the PVA film for demolding comprises the following steps:
the PVA was milled and sieved through an 80 mesh screen or larger.
Has the advantages that: the PVA film for demolding has reasonable recipe, raised water resistance and is suitable for demolding marble.
Detailed Description
The present invention provides a PVA film for mold release and a method for producing the same, and the present invention is described in further detail below in order to make the object, the technical solution and the effect of the present invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The invention provides a PVA film for demoulding, which solves the problem that a high-temperature water-soluble film resists water at 40 ℃ through a reasonable formula. The PVA film for demoulding is a PVA high-temperature water-soluble film which can resist 40 ℃ water and does not swell and 55 ℃ whirling water and does not crack.
Specifically, the PVA film for demolding comprises the following raw materials in percentage by weight:
60-80% of polyvinyl alcohol (PVA), 10-30% of plasticizer, 0.2-1.0% of cross-linking agent, 0.1-1% of heat stabilizer, 2-10% of wet strength agent, 2-10% of water repellent agent and the balance of water.
Preferably, the PVA with alcoholysis degree of more than 99.5% is selected, so that the hot water resistance and the mechanical strength of the film after film formation can be effectively improved. Further, PVA powder with the mesh number of more than 80 is selected as the PVA, the PVA powder with the mesh number of more than 80 can be fully and uniformly melted and plasticized in the granulating process, moisture and a plasticizer are absorbed, the chain connection of PVA winding is opened, crystal grains and phase separation after film forming are reduced, the crystallinity and the compactness of the film are improved, and the water resistance of the film is better.
The plasticizer can be selected from one or two of micromolecular plasticizer or macromolecular plasticizer. The small molecular plasticizer can be selected from monomolecular substances such as polyhydric alcohol and low molecular glucoside; the macromolecular plasticizer can be selected from polyethylene glycol with polymerization degree of above 400, polypropylene glycol and polyglycerol with higher molecular weight. The plasticizer can be one or a combination of more of glycerol, triethanolamine, propylene glycol, caprolactam, trimethylolpropane, polyethylene glycol 400, decaglycerol, polypropylene glycol 400 and the like. Preferably, the combination of small molecules and large molecules is recommended to prevent the plasticizer from being separated out. The plasticizer selects a substance with a structure complementary with PVA, and the structural distribution of the plasticizer in the film is fixed through the combination of large molecules and small molecules (the weight ratio of small molecules to large molecules can be in a range of 0.5 to 1.
The cross-linking agent can be boric acid, borax or aqueous organic titanium cross-linking agent Tyzor 371. Preferably, 371 is recommended in the solution of the invention. The adoption of 371 as a cross-linking agent can well shield the cross-linking of PVA hydroxyl groups, and the water resistance is improved after the cross-linking of PVA molecules.
The heat stabilizer comprises sodium hydroxide. The sodium hydroxide can improve the thermal stability of PVA in the processing process of the PVA film, remove vinyl acetate generated by reaction, prevent thermal degradation, simultaneously dehydrate the PVA, oxidize end groups and improve the hot water resistance of the film. However, since the addition of sodium hydroxide causes coloration of the film, a reducing agent is required to control the color, the addition of a salt of a weak acid and a strong base can be used without affecting other properties, and sodium oxalate has been found through experiments to enhance the alkali resistance of PVA. Therefore, in the scheme of the invention, sodium hydroxide and sodium oxalate are selected as the heat stabilizer, and the weight ratio of the sodium hydroxide to the sodium oxalate is 1-3.
The wet strength agent is a polyamide polyamine epichlorohydrin resin (PPE) or a polyamide epichlorohydrin resin (PAE). The wet strength agent polyamide amide epichlorohydrin is added to enable PVA to form a network structure, has higher strength under the condition of containing water, and improves the tensile strength of PVA after soaking in water, so that the PVA film can be kept from cracking when bearing water-containing substances.
The water repellent agent is self-crosslinking or self-drying resin, such as one or combination of water-based acrylic acid, water-based epoxy resin, water-based urea-formaldehyde resin and water-soluble phenolic resin. The water repellent agent is mainly resin of the second component, and the water resistance and the tensile strength of the PVA film can be improved by adding the water repellent agent.
The invention also provides a preparation method of the PVA film for demolding, which comprises the following steps:
uniformly mixing PVA with a plasticizer, a cross-linking agent, a heat stabilizer, a wet strength agent, a water repellent agent and water by using a high-speed mixer, adding the mixed powder into a single-screw extruder for extrusion granulation, storing the granules for 30-60h by using a sealed tank, extruding and blowing a film by using a film blowing machine, and performing post-treatment and sizing to obtain the PVA film for demolding with the thickness of 20-40 microns.
Preferably, the preparation method of the PVA film for demolding further comprises the following steps:
the PVA was milled and sieved through an 80 mesh screen or larger.
When the particle size of the PVA base material is large, the PVA needs to be ground.
The present invention is further illustrated by the following specific examples.
Example 1:
the PVA film for demolding comprises the following raw materials in percentage by weight:
chuanwei 100-27 PVA (ground powder, 100 meshes, alcoholysis degree 99.8%): 76%, plasticizer: 5% of glycerol and 7% of polyethylene glycol; a crosslinking agent: 0.5 percent of Dupont 371PVA cross-linking agent; heat stabilizer: 0.5% of sodium hydroxide and 0.5% of sodium oxalate; 3% of wet strength agent polyamide polyamine epichlorohydrin resin; water repellent agent: 4% of water-based epoxy resin and the balance of water.
Putting PVA fine powder, a plasticizer, a cross-linking agent, a wet strength agent and a water repellent agent into a high-speed mixer together, mixing for 40 minutes, discharging, adding the powder into a single-screw extruder, extruding and granulating, and adding a water solution mixed with a heat stabilizer into a front-section infiltration area of the extruder. After being made into granules, the granules are placed in a closed container for aging for 48 hours. Extruding the cured granules by a double-screw extruder, blowing a film, performing post-treatment shaping after film discharge, and rolling. The performance test was conducted after leaving for two days under the conditions of 23 ℃ and 45% RH.
Example 2:
the PVA film for demolding comprises the following raw materials in percentage by weight:
sichuan vitamin 100-27 PVA (ground, 120 mesh, alcoholysis degree 99.8%): 72%, plasticizer: 8% of decaglycerol and 7% of triethanolamine; a crosslinking agent: dupont 371PVA cross-linking agent 0.5%; thermal stabilizer: 0.5 percent of sodium hydroxide and 0.5 percent of sodium oxalate; wet strength agent: 3% of polyamide polyamine epichlorohydrin resin; water repellent agent: 4% of water-based acrylic acid and the balance of water.
Putting PVA fine powder, a plasticizer, a cross-linking agent, a wet strength agent and a water repellent agent into a high-speed mixer together, mixing for 40 minutes, discharging, adding the powder into a single-screw extruder, extruding and granulating, and adding a water solution mixed with a heat stabilizer into a front-section infiltration area of the extruder. After being made into granules, the granules are placed in a closed container for aging for 48 hours. Extruding the cured granules by a double-screw extruder, blowing a film, performing post-treatment shaping after film discharge, and rolling. The performance test was performed after two days of standing at 23 ℃,45% rh (relative humidity).
Example 3:
the PVA film for demolding comprises the following raw materials in percentage by weight:
colorado 71-30PVA (hollow micropowder, alcoholysis degree 99.5%): 60%, plasticizer: 12% of trimethylolpropane and 400% of polyethylene glycol; a crosslinking agent: 0.8 percent of borax; heat stabilizer: 0.5% of sodium hydroxide and 0.5% of sodium oxalate; wet strength agent: 5% of polyamide epichlorohydrin resin; water repellent agent: 4% of water-based acrylic acid and the balance of water.
Putting PVA fine powder, a plasticizer, a cross-linking agent, a wet strength agent and a water repellent agent into a high-speed mixer together, mixing for 40 minutes, discharging, adding the powder into a single-screw extruder, extruding and granulating, and adding an aqueous solution mixed with a heat stabilizer into a front-section infiltration area of the extruder. After being made into granules, the granules are placed in a closed container for aging for 48 hours. Extruding the cured granules by a double-screw extruder, blowing a film, performing post-treatment shaping after film discharging, and rolling. The performance test was conducted after leaving for two days under the conditions of 23 ℃ and 45% RH.
Example 4:
the PVA film for demolding comprises the following raw materials in percentage by weight:
vinpocetine BF17H (80 meshes, alcoholysis degree 99.6%): 80%, plasticizer: 4% of trimethylolpropane and 400% of polypropylene glycol; a crosslinking agent: 0.8 percent of borax; thermal stabilizer: 0.5 percent of sodium hydroxide and 0.5 percent of sodium oxalate; wet strength agent: 2.2% of polyamide epichlorohydrin resin; water repellent agent: 3% of water-based urea-formaldehyde resin and the balance of water.
Putting PVA fine powder, a plasticizer, a cross-linking agent, a wet strength agent and a water repellent agent into a high-speed mixer together, mixing for 40 minutes, discharging, adding the powder into a single-screw extruder, extruding and granulating, and adding a water solution mixed with a heat stabilizer into a front-section infiltration area of the extruder. After being made into granules, the granules are placed in a closed container for aging for 48 hours. Extruding the cured granules by a double-screw extruder, blowing a film, performing post-treatment shaping after film discharge, and rolling. The performance test was conducted after leaving for two days under the conditions of 23 ℃ and 45% RH.
Comparative example 5:
the PVA film for demolding comprises the following raw materials in percentage by weight:
vinpocetine BF17 (20 mesh, alcoholysis degree 98.5%): 78%, plasticizer: 4% of trimethylolpropane and 400% of polypropylene glycol; a crosslinking agent: 0.8 percent of borax; the balance being water
PVA fine powder, a plasticizer and a crosslinking agent are slowly put into an aqueous solution with slight stirring. Heating to 90 deg.C, keeping the temperature for 1h, vacuumizing, defoaming, discharging, performing solution casting on a roller, and performing post-treatment and shaping after film discharge. The performance test was conducted after leaving for two days under the conditions of 23 ℃ and 45% RH.
Comparative example 6:
the PVA film for demolding comprises the following raw materials in percentage by weight:
chuanwei 98-20 (20 meshes, alcoholysis degree 98.5%): 75 percent. Plasticizer: 10% of glycerin, 10% of propylene glycol, and a crosslinking agent: borax: 0.5 percent of water and the balance of
And (3) putting the PVA fine powder, the plasticizer and the cross-linking agent into a high-speed mixer, mixing for 40 minutes, discharging, and adding the powder into a single-screw extruder for extrusion granulation. The prepared pellets are aged in a closed container for 48 h. Extruding the cured granules by a double-screw extruder, blowing a film, performing post-treatment shaping after film discharge, and rolling. The performance test was conducted after leaving for two days under the conditions of 23 ℃ and 45% RH.
Comparative example 7:
the PVA film for demolding comprises the following raw materials in percentage by weight:
vinpocetine BF17H (80 meshes, alcoholysis degree 99.6%): 72%, plasticizer: 4% of trimethylolpropane and 7% of propylene glycol; a crosslinking agent: 0.8 percent of borax and the balance of water.
And (3) putting the PVA fine powder, the plasticizer and the cross-linking agent into a high-speed mixer, mixing for 40 minutes, discharging, and adding the powder into a single-screw extruder for extrusion granulation. The prepared granules are aged for 48 hours in a closed container for curing. Extruding the cured granules by a double-screw extruder, blowing a film, performing post-treatment shaping after film discharge, and rolling. The performance test was performed after two days of standing at 23 ℃,45% rh.
The films prepared in examples 1 to 4 and comparative examples 5 to 7 were subjected to a performance test by the following method:
1. and (3) appearance test:
and lifting the membrane block, and observing the uniform state of the membrane block by naked eyes under natural light.
2. Water swelling at 40 ℃:
adding 1000ml of distilled water into a 1000ml beaker, heating the beaker in a water bath kettle at a set temperature of 40 ℃ in a water bath way, immersing a square membrane block cut into 10cm by 10cm into water after the water temperature in the beaker reaches 40 ℃, fishing out the membrane block after 24h, and sucking water to measure the swelling rate.
3. High-temperature water-soluble test:
1000ml of water is contained in a 1000ml beaker, the beaker is placed on a magnetic stirrer with a heating function for heating, when the water temperature reaches 80 ℃, stirring is started, the vortex depth is 200ml, a film block is clamped by a clamping piece with an outer frame of 6cm x 6cm and an inner frame of 5cm x 5cm, the film block is immersed in the water, observation and timing are started, and the time for damaging the film block in the inner frame and the time for completely dissolving the film block in the water are recorded. One sample of the block was tested every 5 ℃ drop until a temperature was measured at which the block did not break at all.
The test data for examples 1-4 and comparative examples 5-7 are shown in table 1.
TABLE 1
| Sample (I) | Appearance of the product | Swelling ratio at 40 ℃ | Temperature without breaking membrane | Complete dissolution temperature |
| Example 1 | Uniform crystal point free | 0.3% | 62℃ | 72℃ |
| Example 2 | Uniform crystal point free | 0.5% | 60℃ | 70℃ |
| Example 3 | Uniform crystal point free | 0.5% | 60℃ | 70℃ |
| Example 4 | No crystal point, light yellow | 0.3% | 64℃ | 73℃ |
| Comparative example 5 | Uniform crystal point free | 30% | 40℃ | 55℃ |
| Comparative example 6 | Polycrystalline point undissolved matter | 30% | 43℃ | 58℃ |
| Comparative example 7 | Polycrystalline spots, oily precipitation | 15% | 50℃ | 64℃ |
In conclusion, the PVA film for demolding has excellent water resistance, can pass the double inspection indexes of warm water swelling at 40 ℃ and no fracture of a film clamping piece at 55 ℃ in the oscillating water, and is suitable for the demolding production of marble; and the film has uniform appearance and no crystal points, so that the surface defects of the marble slab caused by the unevenness of the film surface can be reduced.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (7)
1. A PVA film for demolding is characterized by comprising the following raw materials in percentage by weight:
60-80% of PVA, 10-30% of plasticizer, 0.2-1.0% of cross-linking agent, 0.1-1% of heat stabilizer, 2-10% of wet strength agent, 2-10% of water repellent agent and the balance of water;
PVA powder with the mesh number of more than 80 is selected as the PVA;
the plasticizer is a combination of a micromolecular plasticizer and a macromolecular plasticizer; the small molecular plasticizer is glycerol, triethanolamine, propylene glycol, caprolactam or trimethylolpropane; the macromolecular plasticizer is polyethylene glycol, polypropylene glycol or polyglycerol;
the heat stabilizer comprises sodium hydroxide;
the PVA film for demolding is prepared by extruding and blowing the PVA film through an extruder.
2. The PVA film for mold release according to claim 1, wherein the PVA has an alcoholysis degree of 99.5% or more.
3. The PVA film for mold release according to claim 1, wherein the weight ratio of the small molecule plasticizer to the large molecule plasticizer is from 0.5; the micromolecular plasticizer is a monomolecular substance, and the macromolecular plasticizer is a polymer with the polymerization degree of more than 400.
4. The PVA film for mold release according to claim 1, wherein the heat stabilizer is selected from sodium hydroxide and sodium oxalate, and the weight ratio of the sodium hydroxide to the sodium oxalate is 1-3.
5. The PVA film for mold release according to claim 1, wherein the crosslinking agent is boric acid, borax or an aqueous organic titanium crosslinking agent Tyzor371;
the wet strength agent is polyamide polyamine epichlorohydrin resin or polyamide epichlorohydrin resin;
the water repellent agent is self-crosslinking and self-drying resin; the self-crosslinking and self-drying resin is one or the combination of more than two of water-based acrylic acid, water-based epoxy resin, water-based urea-formaldehyde resin and water-soluble phenolic resin.
6. A method for producing a PVA film for mold release according to any one of claims 1 to 5, comprising the steps of:
mixing PVA with a plasticizer, a cross-linking agent, a heat stabilizer, a wet strength agent, a water repellent agent and water, then carrying out extrusion granulation, sealing, storing and aging the granules for 30-60h, carrying out extrusion film blowing on the granules, and carrying out post-treatment sizing to obtain the PVA film with the thickness of 20-40 mu m for demoulding.
7. The method for producing a PVA film for mold release according to claim 6, comprising the step of:
the PVA was milled and sieved above 80 mesh.
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