JP2007245432A - Resin washing method and resin washed thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin washing method capable of continuously washing off impurities contained in various resins inclusive of a polyvinyl alcoholic resin, capable of easily reducing the amount of impurities up to the target amount of impurities using a reduced amount of a washing liquid and adaptable to the polyvinyl alcoholic resin and another resin. <P>SOLUTION: The washing liquid is allowed to flow in from the washing liquid injection port 5 of an inclined type screw conveyor 1 while supplying a slurry, which contains resin aggregate or a resin in a solid state, to the inclined type screw conveyor 1 from its resin supply port 2 to feed the same upward and discharged from a washing liquid discharge port 6 through the vicinity of the lower part of the inclined type screw conveyor 1 to remove the impurities in the resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin cleaning method for removing impurities in a resin in a solid state.

  Conventionally, various unpurified synthetic resins contain more or less impurities, for example, residual monomers and by-products from polymerization initiators and catalysts used in the manufacturing process. These impurities often cause degradation of resin performance and environmental health problems.

  For example, polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) resin is a water-soluble polymer having excellent film forming properties, adhesive properties, gas barrier properties, particle dispersibility, emulsifying properties, etc. Adhesives for glue, paper, wood, surface strength improvers such as high-quality paper, paperboard and cardboard liner paper, and undercoat agents for release paper, as well as films, binders for various inorganic materials, emulsion stabilizers, suspensions Widely used in a wide range of fields such as dispersion stabilizers for turbid polymerization, but industrially produced polyvinyl alcohol resins are by-produced from polymerization initiators and saponification catalysts used in the production process. In addition, impurities such as initiator decomposition products and sodium acetate are contained. These impurities can cause unpleasant odors such as acetic acid odor of polyvinyl alcohol resins, reduce the heat resistance of polyvinyl alcohol resins, cause seedling inhibition in some applications, and cause skin irritation. It may be viewed as a problem.

  Accordingly, various studies have been made on a cleaning method for removing impurities in the resin and a method for producing a resin with few impurities.

Originally, a method for producing a resin with few impurities seems to be preferable as a fundamental solution, and various proposals have been made, but there are problems that the production conditions are complicated and the apparatus becomes large. For example, in the case of the above-mentioned polyvinyl alcohol-based resin, as a method for saponifying a vinyl ester-based polymer, a critical temperature (Tc) to 300 ° C. of the solvent in a solvent mainly containing alcohol in the absence of a catalyst. Polyvinyl alcohol free from sodium acetate is obtained by saponification under the conditions of the temperature of the solvent, the critical pressure (Pc) of the solvent to 40 MPa, and the reaction fluid density of 0.1 to 0.4 g / cm ^3. Although a manufacturing method has been proposed (see, for example, Patent Document 1), it is difficult to actually implement the apparatus because the apparatus becomes very large.

On the other hand, as a method for cleaning a resin, a method in which a solid-state resin such as a resin chip is placed in a cleaning solution and stirred is relatively simple (for example, see Patent Document 2). Even in the case of the above-mentioned polyvinyl alcohol-based resin, as a method for removing impurities such as sodium acetate contained in the polyvinyl alcohol-based resin, batch cleaning is performed using a solvent in which impurities such as water, methanol, ethanol and the like are dissolved as a cleaning liquid. The method to do is common. However, in order to reduce the amount of impurities by such a method, there is a problem that a large amount of solvent is consumed.
JP 2001-81128 A (Claim 1) JP 2002-102810 A (paragraphs 0016 to 0018)

  In view of the current situation in which there is a need for a method for efficiently reducing impurities contained in a resin with a small amount of cleaning liquid from the circumstances as described above, the present invention eliminates impurities contained in various resins including polyvinyl alcohol resins. To provide a resin cleaning method applicable to polyvinyl alcohol resins and other resins that can be continuously washed and that can easily reduce the impurity amount to a target impurity amount with a small amount of cleaning liquid. Is an issue.

  The present inventors have found that it is possible to remove impurities in the polyvinyl alcohol-based resin by supplying a device capable of extruding the polyvinyl alcohol-based resin and flowing the cleaning liquid from the counterflow direction to the extrusion flow direction. Further studies have been made and the present invention has been completed.

That is, the present invention
[1] An impurity in the resin is removed by flowing a cleaning liquid from a counter-current direction while extruding and flowing a solid-state resin aggregate or a slurry containing the solid-state resin. Characterized resin cleaning method;

[2] A solid state resin aggregate or a slurry containing a solid state resin is supplied from the vicinity of the lower part of the inclined screw conveyor and conveyed upward, and the cleaning liquid is poured from the upper part of the inclined screw conveyor to the vicinity of the lower part. Removing the impurities in the resin by discharging through the resin;

[3] Assembly of resin in a solid state using an apparatus composed of a vertical moving bed apparatus and an inclined screw conveyor, and connected to the lower part of the inclined screw conveyor at the lower part of the vertical moving bed apparatus A slurry containing a solid or solid state resin is supplied from the upper part of the vertical moving bed apparatus, and is transported to the upper side of the inclined screw conveyor via the lower part, while the cleaning liquid is supplied from the vicinity of the upper part of the inclined screw conveyor. A resin washing method characterized by removing impurities in the resin by pouring and discharging from the vicinity of the upper part of the vertical moving bed apparatus; and

[4] The method for cleaning a resin according to any one of [1] to [3] above, wherein the resin is a polyvinyl alcohol resin;

[5] A resin from which impurities have been removed, obtained by washing by the washing method according to any one of [1] to [3] above; and

[6] The present invention relates to a polyvinyl alcohol-based resin from which impurities are removed, which is obtained by washing according to the method described in [4] above.

  The resin cleaning method of the present invention is industrially very advantageous because the amount of impurities can be reduced to the target impurity amount with a small amount of cleaning liquid compared with the conventional resin cleaning method. In addition, since a complicated apparatus is not required, it can be easily incorporated into the current resin manufacturing process. In particular, if used for cleaning polyvinyl alcohol resin, it is suitable as a cleaning method that can remove impurities and reduce acetic acid odor peculiar to polyvinyl alcohol resin. It can be easily incorporated.

  The resin cleaning method of the present invention (hereinafter sometimes referred to as “the present cleaning method”) is a novel method for washing out and removing impurities contained in a resin using a cleaning liquid. Washing is performed while flowing the resin aggregate.

  The term “solid resin” as used in the present invention refers to a resin that is widely in a solid state. For example, when one of the particles is allowed to stand, the shape does not collapse as in a molten state. If it is what. Accordingly, water-containing gels, solvent-containing gels and the like also correspond to “solid state resins”.

  The shape of the resin in the solid state is not particularly limited as long as it can flow as an aggregate or as a slurry. For example, it may be any of prismatic, cylindrical, granular, powdered, flakes, and fibers. There may be. The size is not particularly limited as long as it is in a range from very fine to several centimeters (cm). For example, it may be a fine powder having a diameter of several μm, a sphere having a diameter of several centimeters, or a prism having a square of several centimeters. If it is fluid in the state of an aggregate such as a grain, it may be used for washing as it is, and if it is difficult to flow like a fiber, it may be fluidized as a slurry using an appropriate dispersion medium.

  This cleaning method is applicable to synthetic resins in general, and the resin to be cleaned by this cleaning method is not particularly limited as long as it is in a solid state within a certain temperature range, but under normal working environment (5 ° C. It is preferable that it is in a solid state at about 50 ° C.) because a special device for temperature adjustment is not required.

  This cleaning method is particularly suitable for cleaning polyvinyl alcohol-based resins. There are no restrictions on the physical properties such as polymerization degree, saponification degree, aqueous solution viscosity, polymerization degree distribution, residual acetate group distribution, 1,2-glycol bond amount, stereoregularity, and terminal structure of the polyvinyl alcohol resin that can be used in the present invention. The modification described later may be performed. The form of the polyvinyl alcohol-based resin before washing may be a state in which the saponification solvent is contained immediately after the saponification reaction is performed or in a dried state. It can be used after being cut or crushed, and is not particularly limited.

  Examples of the aliphatic vinyl esters used in producing the polyvinyl alcohol polymer that can be used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl stearate. For this, vinyl acetate is desirable. Examples of the unsaturated monomer containing a cyclic carbonate group include, but are not limited to, vinyl ethylene carbonate, vinylene carbonate, propylene carbonate methacrylate, propylene carbonate acrylic acid, and the like. Further, in addition to the unsaturated monomer containing a cyclic carbonate group within the range not impairing the effects of the present invention, copolymerization of an unsaturated monomer copolymerizable with the aliphatic vinyl ester and an aliphatic vinyl ester is performed. You may go. Examples of unsaturated monomers copolymerizable with aliphatic vinyl esters include unsaturated dibasic acid monoalkyl esters such as monomethyl maleate and monomethyl itaconate, acrylamide, dimethylacrylamide, N-methylolacrylamide, N- Amide group-containing monomers such as vinyl-2-pyrrolidone, alkyl vinyl ethers such as lauryl vinyl ether and stearyl vinyl ether, hydroxyl-containing monomers such as allyl alcohol, dimethylallyl alcohol, isopropenyl allyl alcohol, allyl acetate, dimethylallyl acetate, Acetyl group-containing monomers such as isopropenyl allyl acetate, vinyl halides such as vinyl chloride, vinylidene chloride and vinyl fluoride, trimethoxyvinylsilane, tributylvinylsilane, diphenylmethyl Although vinyl silanes such as vinyl silane, and the like is not limited to this.

  The copolymerization method may be a known one, and examples thereof include a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among them, α, α′-azobis is used in a solvent such as methyl alcohol. An azo or peroxide initiator such as isobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, peracetic acid, di-n-propyl peroxydicarbonate, etc. The polymerization method is generally used. Moreover, a method for removing unreacted monomers and a saponification, drying, pulverization method, etc. may be known methods, and there is no particular limitation.

  The cleaning liquid used for cleaning the resin in the present invention is not particularly limited as long as it is a liquid that can dissolve impurities to be removed in the target resin, and the resin itself completely dissolves during cleaning. Otherwise, the resin may be dissolved somewhat. For example, in the case of washing a polyvinyl alcohol-based resin, methanol, ethanol, toluene, benzene, hexane, water, methyl acetate, acetone, methyl ethyl ketone, and the like can be mentioned. The above may be used together. When removing sodium acetate contained in the polyvinyl alcohol-based resin, it is industrially preferable to use methanol, ethanol, a mixture of methanol and methyl acetate, or a mixture of ethanol and methyl acetate.

  In this cleaning method, the resin aggregate or slurry as described above is extruded and flowed. Needless to say, the extrusion flow does not need to be an ideal extrusion flow, and may be of a level that is normally recognized as the extrusion flow being dominant. A washing apparatus that can be used in the present invention because it can cause such extrusion flow is not particularly limited, and examples thereof include a screw conveyor, a bucket conveyor, a belt conveyor, and a natural sedimentation tank. In particular, the inclined screw conveyor is suitable for use in the present invention because the extrusion flow and stirring and mixing can be performed simultaneously, so that impurities can be easily eluted into the cleaning liquid.

  In the present cleaning method, while the resin aggregate or slurry is extruded and flowed as described above, the cleaning liquid is allowed to flow in a direction opposite to the flow direction of the resin in the cleaning apparatus, that is, a direction in which a so-called countercurrent flow is formed. By flowing the cleaning liquid from the counterflow direction, the cleaning direction is larger than that in the same direction as the resin flow direction, that is, the flow direction is parallel to the flow direction of the polyvinyl alcohol resin. Efficiency is obtained. The cleaning liquid may flow continuously or intermittently, and the supply position of the cleaning liquid is not particularly limited as long as a resin flow and a countercurrent flow can be formed. The washing liquid used for washing can be used again as a washing liquid after the impurities eluted from the resin are separated by an operation such as distillation. In addition, you may add the rinse process which flushes a washing | cleaning liquid with water etc. as needed.

  The amount of cleaning liquid used may be appropriately adjusted depending on the type, shape and amount of resin to be removed, the type and amount of impurities to be removed, the target amount of impurities after cleaning, etc., and is particularly limited However, the range of 0.1 to 50 times the amount of the resin is usually preferred. The contact time between the cleaning liquid and the resin is not particularly limited, but it is preferable to take a contact time of 5 minutes or more in order to improve the effect of removing impurities with a smaller amount of cleaning liquid. For example, in the case of a polyvinyl alcohol-based resin, a preferable result can be obtained by taking a contact time of 5 minutes or more using a cleaning liquid of 0.1 to 50 times the mass of the polyvinyl alcohol-based resin.

  The present inventors consider the reason why the removal efficiency of impurities by this cleaning method is high as follows. That is, in the method of removing impurities in the resin using the cleaning liquid, the impurities in the resin are dissolved in the cleaning liquid at the time of cleaning. Therefore, in batch cleaning and parallel cleaning, the impurity concentration in the resin and the impurity concentration in the cleaning liquid It is difficult to obtain a high concentration gradient. On the other hand, in the present cleaning method in which the flow direction of the resin and the flow direction of the cleaning liquid are countercurrent, the concentration gradient can be increased, in other words, the cleaning liquid in a state where the resin is more fresh. It is because it can touch.

  Therefore, this cleaning method is a cleaning method that can efficiently remove impurities with a small amount of cleaning liquid. Not only cleaning of resin, but also cleaning of glass, rock, wood, pulp, and fibers (fibers other than resin), etc. It can also be applied to.

  Next, a preferred embodiment of this cleaning method will be described in detail with reference to the drawings. First, in the first preferred embodiment, a cleaning apparatus mainly composed of an inclined screw conveyor 1 as shown in FIG. 1 is used. A solid-state resin aggregate to be cleaned or a slurry containing a solid-state resin (hereinafter sometimes referred to as “resin” or the like) is supplied from the vicinity of the lower portion of the inclined screw conveyor 1. Specifically, a resin supply port 2 is provided in the vicinity of the lower part of the inclined screw conveyor 1 so that resin or the like can be introduced, and the resin or the like is supplied from here. The supplied resin is conveyed upward in the inclined screw conveyor 1 by the conveying screw 3.

  On the other hand, the cleaning liquid is allowed to flow from the vicinity of the upper portion of the same inclined screw conveyor 1. Specifically, the cleaning liquid is injected from the cleaning liquid injection port 5 provided in the vicinity of the upper portion of the inclined screw conveyor 1 by normal pressure or pressurization using a metering pump or the like as necessary. The injected cleaning liquid is discharged via the vicinity of the lower part of the inclined screw conveyor 1. Specifically, a cleaning liquid discharge port 6 is provided between the resin supply port 2 and the inclined screw conveyor 1 and discharged. At this time, the liquid level of the cleaning liquid filled in the inclined screw conveyor 1 (represented by a horizontal dotted line in the figure) can be adjusted by the height position of the cleaning liquid discharge port 6. Providing the cleaning liquid discharge port 6 at a height slightly lower than the position of the inlet 5 is preferable because the liquid level can be maintained at a certain level and there is no need to pressurize the cleaning liquid.

  In this way, the flow direction of the resin conveyed upward in the inclined screw conveyor 1 and the flow direction of the cleaning liquid become countercurrent directions, and the resin is washed. The washed resin conveyed above the liquid level is discharged out of the apparatus from the resin discharge port 4 in the vicinity of the upper portion of the inclined screw conveyor 1. If necessary, two or more stages of this apparatus may be connected in series for cleaning, and in that case, a plurality of types of impurities can be removed in a continuous process by changing the cleaning liquid. It is also possible to rinse the cleaning solution used in the previous apparatus.

  Next, as a second preferred embodiment, a cleaning device comprising a vertical moving bed device 7 and an inclined screw conveyor 1 as shown in FIG. 2 is used. In this cleaning apparatus, since the lower part of the vertical moving bed apparatus 7 is coupled to the vicinity of the lower part of the inclined screw conveyor 1, the resin that has moved from the upper part to the lower part of the vertical moving bed apparatus 7 is the same. The apparatus is automatically supplied to the inclined screw conveyor 1 and conveyed upward by the conveying screw 3. That is, resin or the like is supplied from the upper part of the vertical moving bed apparatus 7 and conveyed to the upper part of the inclined screw conveyor 1 via the lower part of the apparatus. This configuration is preferable because the amount of the resin held in the cleaning device can be increased to clean a large amount and the contact time between the resin and the cleaning liquid can be increased.

  The vertical moving bed apparatus 7 is generally cylindrical and preferably has a cross-sectional shape that is circular in terms of processing of the main body or uniform temperature distribution in the layer, but is short, polygonal, elliptical, etc. Any shape is acceptable. In addition, various shapes such as those in which the apparatus diameter does not change in the vertical direction depending on the location, those with a gradient in the lower part, those in which the lower part is squeezed are conceivable, but it is sufficient if the model is a saddle type, There is no particular limitation. The size of the vertical moving bed apparatus 7 is not particularly limited, and an appropriate size may be used in consideration of the balance with the inclined screw conveyor 1.

  The vertical moving bed device 7 may not have a mechanical stirring device, but it is preferable to provide a stirring blade 8 as the mechanical stirring device because the piston flow property can be improved. As the stirring blade 8, it is preferable to attach at least two or more blades in series in order to improve the piston flow property, and the propeller blade, the disk type turbine blade, or the like is effective as the shape. From the standpoint of enhancing the piston flow, it is preferable that the cross-sectional area or inner diameter of the vertical moving bed apparatus 7 is as small as possible.

  When the apparatus shown in FIG. 2 is used, resin or the like is supplied from the upper part of the vertical moving bed apparatus 7, specifically from the resin supply port 2 provided at the upper part of the vertical moving bed apparatus 7. As described above, the supplied resin flows downward in the vertical moving bed apparatus 7, enters the inclined screw conveyor 1 via the lower part of the apparatus, and is inclined by the conveying screw 3. The inside is conveyed upward.

  On the other hand, from the vicinity of the upper part of the inclined screw conveyor 1, specifically, from the cleaning liquid inlet 5 provided in the vicinity of the upper part of the inclined screw conveyor 1, the cleaning liquid is subjected to normal pressure or pressurization using a metering pump or the like as necessary. Inject. The injected cleaning liquid flows downward of the inclined screw conveyor 1, enters the vertical moving bed apparatus 7 via the vicinity of the lower part of the conveyor, flows upward through the apparatus, and near the upper part of the apparatus Specifically, the liquid is discharged from the cleaning liquid discharge port 6 provided on the side wall near the top.

  In the apparatus shown in FIG. 2 as well, as in the apparatus shown in FIG. 1, the liquid level of the cleaning liquid filled in the inclined screw conveyor 1 and the vertical moving bed apparatus 7 depending on the height position of the cleaning liquid discharge port 6. (Represented by a horizontal dotted line in the figure) can be adjusted.

  Thus, the flow direction of the resin moving downward in the vertical moving bed apparatus 7, the flow direction of the resin conveyed upward in the inclined screw conveyor 1, and the flow direction of the cleaning liquid are determined as follows. In both the apparatus 7 and the inclined screw conveyor 1, the resin is washed in the counterflow direction. The washed resin transported above the liquid level in the inclined screw conveyor 1 is discharged out of the apparatus from the resin discharge port 4 near the upper portion of the inclined screw conveyor 1.

  As described above, according to the present cleaning method, impurities of the resin can be efficiently removed. Therefore, the resin obtained by cleaning by the present cleaning method has a small content with impurities removed. Therefore, the value as a product increases.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples. In the following Examples and Comparative Examples, “part” and “%” mean mass basis unless otherwise specified. In addition, the characteristic of the polyvinyl alcohol-type resin as described in a following example and a comparative example is measured thru | or evaluated with the following method.

[Measurement and evaluation method of resin properties]
(1) Degree of polymerization, degree of saponification, amount of sodium acetate, and volatile matter were measured according to JISK 6726.
(2) The degree of modification of maleic acid-modified polyvinyl alcohol was measured by a known potentiometric titration method using an automatic potentiometric titrator (manufactured by Kyoto Electronics Industry Co., Ltd., “AT-420 (trade name)”).
(3) The ethylene content of ethylene-modified polyvinyl alcohol was determined by a known NMR analysis method using a nuclear magnetic resonance (NMR) apparatus (manufactured by Varian, “UNITY INOVA600 (trade name)”).

Moreover, the polyvinyl alcohol-type resin used as a resin sample for washing | cleaning of Examples 1, 2 and Comparative Examples 1-3 was manufactured with the following method.
[Production example of polyvinyl alcohol resin]
A reactor equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and pressure gauge was purged with nitrogen, and then 2800 parts by mass of deoxygenated vinyl acetate monomer and 800 parts by mass of methanol were charged, and heating was started under stirring. When the internal temperature reached 60 ° C., an initiator solution prepared by dissolving 1 part by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) as an initiator in 50 parts by mass of methanol was added separately. Then, polymerization was started. After polymerization at 60 ° C. for 5 hours, the polymerization was stopped by cooling. The solid concentration in the polymerization solution at this time was 55.1%. While supplying the obtained polymerization solution to a demonomer tower having a multi-stage perforated plate in the tower, methanol vapor was blown from the bottom of the tower, and the polymerization solution was brought into contact with methanol vapor, thereby allowing unreacted vinyl acetate monomer. Was removed. The solid content concentration of the polyvinyl acetate-methanol solution after removing the vinyl acetate monomer was 42%. The temperature of this polyvinyl acetate-methanol solution was kept at 40 ° C., and sodium hydroxide was added to carry out a saponification reaction to obtain a polyvinyl alcohol resin. The form of the polyvinyl alcohol resin at the end of the saponification reaction was a solid gel containing methanol as a solvent and methyl acetate as a by-product, and the degree of saponification was 88 mol% and the volatile content was 58%. . Further, the content of sodium acetate as a by-product was 0.8% of the solid content of the polyvinyl alcohol resin. The gel-like polyvinyl alcohol resin crushed to a size of 3 mm square was used as a cleaning resin sample.

[Example 1]
From the resin supply port 2 of the apparatus shown in FIG. 2, a cleaning resin sample made of the gel-like polyvinyl alcohol resin produced in the production example of the polyvinyl alcohol resin was continuously supplied at a rate of 200 g / min. The time required for the cleaning resin sample entering the resin supply port 2 to come out of the resin discharge port 4 was 30 minutes. In parallel with the supply of the resin sample, methanol as a cleaning liquid was allowed to flow from the cleaning liquid inlet 5 at a flow rate of 50 g / min and discharged from the cleaning liquid outlet 6. One hour after starting the supply of the resin sample, the resin sample after washing was collected from the resin outlet 4 and the amount of sodium acetate in the polyvinyl alcohol was measured. It was found that it had dropped to 3%.

[Example 2]
From the resin supply port 2 of the apparatus shown in FIG. 1, a cleaning resin sample made of the gel-like polyvinyl alcohol resin produced in the production example of the polyvinyl alcohol resin was continuously supplied at a rate of 500 g / min. The time required for the cleaning resin sample entering the resin supply port 2 to come out of the resin discharge port 4 was 20 minutes. In parallel with the supply of the resin sample, methanol as a cleaning liquid was allowed to flow from the cleaning liquid inlet 5 at a flow rate of 500 g per minute and discharged from the cleaning liquid outlet 6. One hour after starting the supply of the resin sample, the resin sample after washing was collected from the resin outlet 4 and the amount of sodium acetate in the polyvinyl alcohol was measured. It decreased to 1%.

[Example 3]
Polyvinyl alcohol resin having a maleic acid modification degree of 2.0 mol%, a polymerization degree of 1700, a saponification degree of polyvinyl alcohol part of 96 mol%, a volatile content of 5% and a sodium acetate content of 1.1% is 3 mm square. The crushed powder was used as a cleaning resin sample. The cleaning resin sample was continuously supplied from the resin supply port 2 of the same apparatus shown in FIG. The time required for the cleaning resin sample entering the resin supply port 2 to come out of the resin discharge port 4 was 30 minutes. In parallel with the supply of the resin sample, methanol as a cleaning liquid was allowed to flow from the cleaning liquid inlet 5 at a flow rate of 300 g / min and discharged from the cleaning liquid outlet 6. One hour after the start of resin sample supply, the resin sample after washing was collected from the resin outlet 4 and the amount of sodium acetate was measured. It turns out that it is falling.

[Example 4]
Ethylene-modified polyvinyl alcohol resin having a polymerization degree of 1500% by copolymerization of ethylene, a saponification degree of polyvinyl alcohol part of 99 mol%, a volatile content of 4%, and a sodium acetate content of 1.3% is 3 mm square. The pulverized product was used as a cleaning resin sample. This washing resin sample was continuously supplied at a rate of 150 g / min from the resin supply port 2 of the same apparatus shown in FIG. The time required for the cleaning resin sample entering the resin supply port 2 to come out of the resin discharge port 4 was 25 minutes. In parallel with the supply of the resin sample, methanol as a cleaning liquid was allowed to flow from the cleaning liquid inlet 5 at a flow rate of 400 g / min and discharged from the cleaning liquid outlet 6. One hour after the start of the resin sample supply, the resin sample after washing was collected from the resin outlet 4 and the amount of sodium acetate was measured. It turns out that it is falling.

[Comparative Example 1]
Into a 2 L beaker, 500 g of a washing resin sample made of the gel-like polyvinyl alcohol resin produced in the production example of the polyvinyl alcohol resin was added, 500 g of methanol as a washing liquid was added, and 20 minutes using a stirrer having a turbine blade. Washing was carried out batchwise by stirring (rotation number: 60 rpm). The amount of sodium acetate in the polyvinyl alcohol after washing taken out from the beaker was measured and found to be 0.5%.

[Comparative Example 2]
The cleaning apparatus comprising the gel-like polyvinyl alcohol resin produced in the production example of the polyvinyl alcohol resin from the resin supply port 2 in the state where the washing liquid discharge port 6 of the apparatus shown in FIG. The resin sample for use was continuously fed at a rate of 200 g / min. The time required for the cleaning resin sample entering the resin supply port 2 to come out of the resin discharge port 4 was 30 minutes. In parallel with the supply of the resin sample, methanol as a cleaning liquid was allowed to flow from the resin supply port 2 at a flow rate of 50 g per minute. At this time, since the cleaning liquid discharge port 6 is in a closed state, the cleaning resin sample and the cleaning liquid are discharged in parallel from the resin discharge port 4. One hour after starting the supply of the resin sample, the resin sample after washing was collected from the resin outlet 4 and the amount of sodium acetate in the polyvinyl alcohol was measured and found to be 0.7%.

[Comparative Example 3]
In the state where the waste cleaning liquid discharge port 6 of the same apparatus shown in FIG. 1 as used in Example 2 is closed, the resin supply port 2 is made of the gel-like polyvinyl alcohol resin produced in the production example of the polyvinyl alcohol resin. The washing resin sample was continuously supplied at a rate of 500 g / min. The time required for the cleaning resin sample entering the resin supply port 2 to come out of the resin discharge port 4 was 20 minutes. In parallel with the supply of the resin sample, methanol as a cleaning liquid was allowed to flow from the resin supply port 2 at a flow rate of 500 g per minute. At this time, since the cleaning liquid discharge port 6 is in a closed state, the cleaning resin sample and the cleaning liquid are discharged in parallel from the resin discharge port 4. One hour after starting the supply of the resin sample, the washed polyvinyl alcohol was collected from the resin outlet 4, and the amount of sodium acetate was measured.

  From the above results, the cleaning methods of the present invention in Examples 1 to 4 were able to efficiently remove sodium acetate, which is an impurity in polyvinyl alcohol, as compared with the cleaning method by batch cleaning or parallel flow cleaning of the comparative example. Recognize.

  The vertical moving bed apparatus and the inclined screw conveyor used in the embodiment will be described. The vertical moving bed apparatus used in the embodiment 1 has a cylindrical body, and is located above the lower inclined portion. The length (height) was 60 cm, the inner diameter was 180 mm, and the amount of cleaning liquid stored in the main body was 15.3 L. The main body of the inclined screw conveyor used in combination with this was 1.6 m, the inner diameter was 50 mm, and the inclination angle was 45 degrees.

  The main body of the inclined screw conveyor used in Example 2 had a total length of 2 m, an inner diameter of 104 mm, an inclination angle of 15 degrees, and the amount of cleaning liquid stored in the main body at the time of inclination was 7 L.

It is a longitudinal cross-sectional view which shows the schematic whole structure of the washing | cleaning apparatus used in one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the schematic whole structure of the washing | cleaning apparatus used in other embodiment of this invention.

Explanation of symbols

1 Inclined Screw Conveyor 2 Resin Supply Port 3 Conveying Screw 4 Resin Discharge Port 5 Cleaning Liquid Injection Port 6 Cleaning Liquid Discharge Port 7 Vertical Moving Bed Device 8 Stirring Blade

Claims (6)

  While extruding a solid resin aggregate or a slurry containing a solid resin, the impurities in the resin are removed by flowing a cleaning liquid from a direction opposite to the extrusion flow direction. Resin cleaning method.   While supplying an aggregate of solid resin or slurry containing solid resin from the vicinity of the lower part of the inclined screw conveyor and conveying it upward, the cleaning liquid is poured from the upper part of the inclined screw conveyor and passed through the vicinity of the lower part. The resin cleaning method is characterized in that impurities in the resin are removed by discharging the resin.   An assembly of solid resin or solid using a device comprising a vertical moving bed device and an inclined screw conveyor, and a lower portion of the vertical moving bed device combined with the vicinity of the lower portion of the inclined screw conveyor. The slurry containing the resin in a state is supplied from the upper part of the vertical moving bed apparatus, and while being conveyed to the upper side of the inclined screw conveyor via the lower part, the cleaning liquid is poured from the vicinity of the upper part of the inclined screw conveyor. A resin cleaning method, wherein impurities in the resin are removed by discharging from the vicinity of the upper part of the vertical moving bed apparatus.   The resin cleaning method according to any one of claims 1 to 3, wherein the resin is a polyvinyl alcohol resin.   A resin from which impurities have been removed, obtained by washing by the washing method according to any one of claims 1 to 3. A polyvinyl alcohol-based resin from which impurities have been removed, obtained by washing by the washing method according to claim 4.

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