Thermoplastic polyvinyl alcohol resin and preparation method thereof

Abstract

The invention discloses thermoplastic polyvinyl alcohol resin which is prepared from the following raw materials: polyvinyl alcohol, a plasticizer, soft water and a processing aid, the mosquito-repellent incense further comprises raw materials including a deodorant. The hot processing fluidity of the polyvinyl alcohol resin can be improved, the acid smell volatilized by small molecules generated by degradation of the thermoplastic polyvinyl alcohol resin after hot processing can be reduced, migration of a plasticizer in the placement process of the polyvinyl alcohol film is hindered, seepage of the plasticizer is reduced, and the service life of the polyvinyl alcohol film is prolonged. Therefore, the smoothness and comfort of the thermoplastic PVA resin in storage and actual use are improved.

Description

Technical Field

[0001] The invention relates to polyvinyl alcohol, in particular to a thermoplastic polyvinyl alcohol resin and a preparation method thereof. Background Art

[0002] Polyvinyl alcohol (PVA) is a water-soluble polymer with the characteristics of good density, high crystallinity, strong adhesion, flexible and smooth film, oil resistance, solvent resistance, abrasion resistance, good gas barrier properties, and water resistance after special treatment. It has a wide range of uses. Polyvinyl alcohol is non-toxic, odorless, and harmless to the human body. It has good affinity with the natural environment, does not accumulate, and does not pollute. Therefore, it is widely used in chemical packaging, washing packaging, water transfer printing, embroidery, textile packaging, food packaging, electronic and electrical product packaging and other fields.

[0003] At present, most polyvinyl alcohol films are produced by solution casting, which obtains polyvinyl alcohol raw materials and a certain amount of water. After two steps of casting coating and drying (heat treatment), the finished polyvinyl alcohol film can be obtained by peeling and winding. The process is very simple and easy to operate, which is an efficient production method. However, the product quality is not easy to control, the film output rate is low, the energy consumption is high, and the equipment investment is large. Therefore, the market expects a more convenient thermoplastic processing extrusion blown film method.

[0004] However, polyvinyl alcohol is a crystalline polymer with a large number of hydroxyl groups in its molecules, which can form a large number of intramolecular and intermolecular hydrogen bonds, making its melting point as high as 200-240°C, while its decomposition temperature is low. It begins to dehydrate at 160°C, begins to decompose at 200°C, and is completely decomposed at 220°C. The melting point and decomposition temperature of PVA are close, making it difficult to directly perform thermoplastic processing.

[0005] Most of the technologies at home and abroad are to weaken the hydrogen bonding forces within and between polyvinyl alcohol molecules through copolymerization or adding plasticizers to blend, lower its melting point, make it thermoplastic processable, and thus obtain melt-processable modified polyvinyl alcohol resin or polyvinyl alcohol blended modified resin.

[0006] Chinese patent document CN105440522A discloses a thermoplastic polyvinyl alcohol resin and a preparation method thereof, which is composed of an effective amount of polyvinyl alcohol, a plasticizer, soft water and a processing aid, wherein the degree of polymerization of the polyvinyl alcohol is 1000-2400, 72 (mol)% ≤ alcoholysis degree < 90 (mol)%, the plasticizer is at least one of glycerol, polyethylene glycol, and triethylene glycol diisooctanoate, and the processing aid is at least one of talc, silicon dioxide, oleamide, and saturated aliphatic dicarboxylic acid ester.

[0007] Japanese patent document JP H06240089 A discloses a polyvinyl alcohol composition, which comprises 0.01-20 parts by weight of bentonite or 0.01-10 parts by weight of alkaline earth metal hydroxide such as magnesium hydroxide and 100 parts by weight of polyvinyl alcohol with a saponification degree of 20-98 mol %; the composition has excellent oil resistance, solvent resistance, toughness, tear strength, transparency and antistatic properties, as well as excellent water resistance. It also has functions such as disintegration and biodegradability, and does not produce acetic acid odor during hot melt molding.

[0008] The thermoplastic polyvinyl alcohol resin prepared in the above prior art is not smooth and comfortable during storage and actual use. Summary of the invention

[0009] The invention provides a thermoplastic polyvinyl alcohol resin and a preparation method thereof, which can increase the smoothness and comfort of the thermoplastic polyvinyl alcohol resin during storage and actual use by reducing the precipitation of a plasticizer.

[0010] On the one hand, the present invention provides a thermoplastic polyvinyl alcohol resin, which is processed from raw materials including polyvinyl alcohol, a plasticizer, soft water and a processing aid; and also processed from raw materials including a deodorant.

[0011] Furthermore, the deodorant includes cyclodextrin or a derivative thereof.

[0012] Furthermore, the deodorant is selected from one or more of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, hydroxypropyl-β-cyclodextrin and xanthobutyl-β-cyclodextrin.

[0013] Furthermore, the ratio of the amount of the added deodorant to the amount of polyvinyl alcohol is 0.1-50:50-90, in parts by mass.

[0014] Furthermore, it is prepared from the following raw materials in parts by weight: the ratio of the added polyvinyl alcohol to the plasticizer is 50-90:10-40, calculated in parts by mass.

[0015] Furthermore, the plasticizer is one or more of pentaerythritol, glycerol, polyethylene glycol, and dipropylene glycol.

[0016] Furthermore, the processing aid is one or more of titanium dioxide, talc, silicon dioxide, oleamide, erucamide, ethylene bisstearamide, and polyethylene oxide.

[0017] Furthermore, the polyvinyl alcohol is a polyvinyl alcohol with a polymerization degree of 1000-2400 and a degree of alcoholysis of 72 mol%≤99 mol%.

[0018] In a second aspect, the present invention provides a method for preparing the thermoplastic polyvinyl alcohol resin of the present invention, comprising the following steps: (1) mixing polyvinyl alcohol, plasticizer, soft water, deodorant and processing aid and heating to 25-90° C. for 0-10 hours; (2) The material obtained in step (1) is conveyed to a screw extruder, melt-extruded at 120-200° C., cooled to 20-40° C., and pelletized by a pelletizer to obtain a thermoplastic polyvinyl alcohol resin.

[0019] The present invention has the following beneficial effects: 1) The thermoplastic polyvinyl alcohol resin of the present invention uses cyclodextrin and its derivatives as deodorants, which can not only increase the hot processing fluidity of the polyvinyl alcohol resin, but also reduce the sour taste of small molecules volatilized by the degradation of the thermoplastic polyvinyl alcohol resin after hot processing, and hinder the migration of plasticizers in the placement process of the polyvinyl alcohol film, reduce the exudation of plasticizers, thereby increasing the smoothness and comfort of the thermoplastic PVA resin during storage and actual use.

[0020] 2) After adding the deodorant to the thermoplastic polyvinyl alcohol resin of the present invention, the produced particles can still be guaranteed to be colorless, transparent, non-yellowing, smooth and non-greasy, and will not affect the quality of the polyvinyl alcohol resin.

[0021] 3) The thermoplastic polyvinyl alcohol resin of the present invention can be prepared into a film by blow molding, melt extrusion-biaxial stretching, melt extrusion-casting, etc., and further used in various fields, including but not limited to soft packaging, toys, hydrogel film, and 3D printing water-soluble film. DETAILED DESCRIPTION

[0022] The examples are provided to better illustrate the content of the present invention, but the content of the present invention is not limited to the examples. Therefore, those skilled in the art can make non-essential improvements and adjustments to the implementation scheme according to the above content of the invention, which still fall within the protection scope of the present invention.

[0023] The raw material composition and mass percentage of the thermoplastic polyvinyl alcohol described in the present invention are: 50-90 parts of polyvinyl alcohol, 10-30 parts of soft water, 10-40 parts of plasticizer, 0.1-50 parts of deodorant and 0.1-15 parts of processing aid; preferably, the raw material composition and mass percentage of the thermoplastic polyvinyl alcohol are: 60-85 parts of polyvinyl alcohol, 5-20 parts of soft water, 20-40 parts of plasticizer, 1-15 parts of deodorant and 1-15 parts of processing aid.

[0024] A method for preparing a thermoplastic polyvinyl alcohol resin film is as follows: (1) polyvinyl alcohol, plasticizer, softener, deodorant, and processing aid are mixed in a high-speed mixer and heated to 25-90° C. for 0-10 hours; (2) conveying the material of step (1) to a screw extruder, melting and extruding at a temperature of 120-200° C., cooling to 20-40° C., and pelletizing and molding with a pelletizer to obtain a thermoplastic polyvinyl alcohol resin; (3) The resin particles prepared in step (2) are conveyed to a screw extruder, and blow molded at a die temperature of 120-200° C. to obtain a thermoplastic polyvinyl alcohol film.

[0025] The test method involved in the present invention is as follows: 1. Melt index test: According to the flow characteristics of thermoplastic polyvinyl alcohol resins of different PVA grades, a melt index meter is used to measure the mass value of the plastic melt flowing through a standard capillary within 10 minutes at a certain temperature and constant pressure, in units of g / 10min. This test method sets the temperature: 120℃-180℃; pressure: 2.16kg-10kg.

[0026] 2. Determination of oil permeability of blown film: Lay the film flat on a glass plate, place 60*90mm oil-absorbing paper close to the film, and then cover it with a layer of PE film. Press it flat with a heavy object and keep it for 24 hours. The total amount of oil-absorbing paper before and after weighing is different. The oil permeability calculation formula is: Oil penetration rate = (m2-m1) / m1 Where m1 represents the original weight of the oil-absorbing paper; m2 represents the weight of the oil-absorbing paper after absorbing the plasticizer.

[0027] 4. Sour taste assessment: identified through human scent organs.

[0028] Example 1 A method for preparing a thermoplastic polyvinyl alcohol resin is: 90 parts of polyvinyl alcohol (polymerization degree 1000, alcoholysis degree 72.0 mol%), 10 parts of polyethylene glycol, 10 parts of soft water, 0.1 parts of α-cyclodextrin and 0.1 parts of oleic acid amide are mixed by a high-speed mixer and heated to 30°C for 2 hours; the obtained material is conveyed to a screw extruder, melt-extruded at a temperature of 180°C, cooled to 40°C, and pelletized by a pelletizer to obtain a thermoplastic polyvinyl alcohol resin; the prepared resin particles are conveyed to a screw extruder, hollow blown at 170°C with a die temperature of 170°C to obtain a thermoplastic polyvinyl alcohol film.

[0029] Example 2 A method for preparing a thermoplastic polyvinyl alcohol resin is: 70 parts of polyvinyl alcohol (polymerization degree 1500, alcoholysis degree 88.0 mol%), 25 parts of triethylene glycol diisooctanoate, 20 parts of soft water, 25 parts of β-cyclodextrin and 7.5 parts of erucamide are mixed by a high-speed mixer and heated to 48°C for 4 hours; the obtained material is conveyed to a screw extruder, melt-extruded at a temperature of 160°C, cooled to 30°C, and pelletized by a pelletizer to obtain a thermoplastic polyvinyl alcohol resin; the prepared resin particles are conveyed to a screw extruder, hollow blown at 160°C with a die temperature of 160°C to obtain a thermoplastic polyvinyl alcohol film.

[0030] Example 3 A method for preparing a thermoplastic polyvinyl alcohol resin is: 50 parts of polyvinyl alcohol (polymerization degree 1200, alcoholysis degree 99 mol%), 25 parts of dipropylene glycol, 20 parts of soft water, 50 parts of gamma-cyclodextrin and 15 parts of erucamide are mixed by a high-speed mixer and heated to 70°C for 8 hours; the obtained material is conveyed to a screw extruder, melt-extruded at a temperature of 150°C, cooled to 25°C, and pelletized and molded by a pelletizer to obtain a thermoplastic polyvinyl alcohol resin; the prepared resin particles are conveyed to a screw extruder, hollow blown at 165°C and a die temperature of 170°C to obtain a thermoplastic polyvinyl alcohol film.

[0031] Example 4 A method for preparing a thermoplastic polyvinyl alcohol resin is: 60 parts of polyvinyl alcohol (polymerization degree 2000, alcoholysis degree 90 mol%), 40 parts of polyethylene glycol, 25 parts of soft water, 10 parts of hydroxypropyl-β-cyclodextrin and 7 parts of polyethylene oxide are mixed by a high-speed mixer and heated to 80°C for 3 hours; the obtained material is conveyed to a screw extruder, melt-extruded at a temperature of 155°C, cooled to 20°C, and pelletized by a pelletizer to obtain a thermoplastic polyvinyl alcohol resin; the prepared resin particles are conveyed to a screw extruder, hollow blown at 160°C and a die temperature of 170°C to obtain a thermoplastic polyvinyl alcohol film.

[0032] Example 5 A method for preparing a thermoplastic polyvinyl alcohol resin is: 70 parts of polyvinyl alcohol (polymerization degree 2400, alcoholysis degree 99 mol%), 35 parts of propylene glycol, 30 parts of soft water, 5 parts of xanthobutyl-β-cyclodextrin and 1 part of talcum powder are mixed by a high-speed mixer and heated to 90°C for 1 hour; the obtained material is conveyed to a screw extruder, melt-extruded at a temperature of 140°C, cooled to 20°C, and pelletized by a pelletizer to obtain a thermoplastic polyvinyl alcohol resin; the prepared resin particles are conveyed to a screw extruder, hollow blown at 168°C and a die temperature of 170°C to obtain a thermoplastic polyvinyl alcohol film.

[0033] Comparative Example 1 Compared with Example 1, no α-cyclodextrin was added.

[0034] Comparative Example 2 Compared with Example 1, α-cyclodextrin is replaced by porous silica.

[0035] The test results of the thermoplastic polyvinyl alcohol resins obtained in the above examples and comparative examples are as follows: Table 1 As can be seen from Table 1 above, Examples 1-5 of the present invention use a specific method of adding a deodorant of cyclodextrin or its derivatives to prepare a thermoplastic polyvinyl alcohol resin, while Comparative Example 1-2 does not use this method, but does not add a deodorant of cyclodextrin or its derivatives or selects other deodorants. The results obtained show that the sour taste of Examples 1-5 is light or no sour taste, the permeability is 10.1-23.1%, and the melt index is 3.74-5.12 g / 10min; the sour taste of Comparative Example 1-2 is strong sour taste, the permeability is 50.2-58.3%, and the melt index is 0.98-2.12 g / 10min. It can be seen that the technical solution of adding cyclodextrin or its derivatives as a deodorant in the preparation of thermoplastic polyvinyl alcohol resin can enable the prepared thermoplastic polyvinyl alcohol resin to hinder the migration of plasticizers during the placement of the polyvinyl alcohol film and reduce the exudation of plasticizers, thereby increasing the smoothness and comfort of the thermoplastic PVA resin during storage and actual use; and reducing the sour smell of small molecules volatile produced by the degradation of the thermoplastic polyvinyl alcohol resin after thermal processing and improving the fluidity of the resin during the thermal processing process.

[0036] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A thermoplastic polyvinyl alcohol resin, comprising raw materials including polyvinyl alcohol, a plasticizer, soft water and a processing aid; characterized in that: It also includes products processed from raw materials including deodorants.

2. The thermoplastic polyvinyl alcohol resin according to claim 1, characterized in that: The deodorant includes cyclodextrin or a derivative thereof.

3. The thermoplastic polyvinyl alcohol resin according to claim 1, characterized in that: The deodorant is selected from one or more of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, hydroxypropyl-β-cyclodextrin and xanthobutyl-β-cyclodextrin.

4. The thermoplastic polyvinyl alcohol resin according to claim 1, 2 or 3, characterized in that: The ratio of the amount of the added deodorant to the amount of the polyvinyl alcohol is 0.1-50:50-90, calculated in parts by mass.

5. The thermoplastic polyvinyl alcohol resin according to claim 1, characterized in that: The ratio of the added polyvinyl alcohol to the plasticizer is 50-90:10-40, calculated in parts by mass.

6. The thermoplastic polyvinyl alcohol resin according to claim 5, characterized in that: The plasticizer is one or more of pentaerythritol, glycerol, polyethylene glycol and dipropylene glycol.

7. The thermoplastic polyvinyl alcohol resin according to claim 5 or 6, characterized in that: The processing aid is one or more of titanium dioxide, talc, silicon dioxide, oleamide, erucamide, ethylene bisstearamide, and polyethylene oxide.

8. The thermoplastic polyvinyl alcohol resin according to claim 5, 6 or 7, characterized in that: The polyvinyl alcohol has a polymerization degree of 1000-2400 and an alcoholysis degree of 72 mol%≤99 mol%.

9. A method for preparing the thermoplastic polyvinyl alcohol resin according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Mix polyvinyl alcohol, plasticizer, softener, deodorant and processing aid and heat to 25-90° C. for 0-10 hours; (2) The material obtained in step (1) is conveyed to a screw extruder, melt-extruded at 120-200° C., cooled to 20-40° C., and pelletized by a pelletizer to obtain a thermoplastic polyvinyl alcohol resin.

Images