JP2023059935A - Polyvinyl alcohol, protective solution containing the same, and polyvinyl acetate emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyvinyl alcohol, a protective solution containing the same, and a polyvinyl acetate emulsion.

SOLUTION: A polyvinyl alcohol of the invention has a ratio (B): (B)=g⁽²⁾-1(τ=100 μs)/g⁽²⁾-1(τ=0.5 μs), which is obtained by measuring a polyvinyl alcohol solution of 6.4 wt.% by a dynamic light scattering (DLS) device. The ratio (B) has a range of 0<(B)<0.38. The polyvinyl alcohol of the invention has a good protective colloid effect, allows reduction in the amount of use of the polyvinyl alcohol, and has relatively stable emulsion viscosity.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to block polymers suitable as dispersants for protective colloid solutions, and more particularly to polyvinyl alcohol as protective colloid and protective solutions and emulsions containing the same.

Polyvinyl alcohol (POLYVINYL ALCOHOL, PVA) is a white or pale yellow granular or powdery substance, a stable, non-toxic, water-soluble polymer. Polyvinyl alcohol has good film-forming properties, and the film formed has excellent adhesion, solvent resistance, friction resistance, tensile strength, and oxygen barrier properties. In a very wide range of products such as adhesives for temporary fixing in screen printers and protective colloids and suspension stabilizers for emulsions such as polyvinyl acetate (PVAc), polyvinyl chloride (PVC) and polystyrene (PS) It is used.

Polyvinyl alcohol has two types of functional groups, a hydrophilic group and a hydrophobic group, at the same time. Therefore, polyvinyl alcohol has surface-active properties and can be used as a protective colloid for polymer emulsification and suspension polymerization reactions. Agglomeration of particles in liquid dispersions can be retarded or prevented. Suspension polymerization reactions typically disperse the target monomer (such as PVAc, PVC or PS) in an aqueous medium in the presence of polyvinyl alcohol as a dispersing agent. The properties of the polyvinyl alcohol have a considerable impact on the quality of the product produced by the target monomer, for example whether PVC can produce the required particle size and particle size distribution, or PVAc the required emulsion viscosity and It affects whether viscosity stability can be generated or not.

Analysis of a conventional polyvinyl alcohol aqueous solution with a dynamic light scattering (DLS) device reveals aggregation in some of the polyvinyl alcohol molecular chains, but this aggregation reduces the properties of the emulsion. put away.

The present invention found that whether polyvinyl alcohol produces large particle aggregation in aqueous solution is related to block length and degree of branching, and this aggregation phenomenon also affects emulsion stability and protective colloid properties. bottom. Therefore, in the present invention, polyvinyl alcohol having a specific particle size ratio range is obtained by controlling the polyvinyl alcohol polymer and alkalizing conditions to obtain polyvinyl alcohol having high protective colloid properties.

In view of this, the main object of the present invention is to provide polyvinyl alcohol, which has a ratio (B), ratio (B)=g ⁽²⁾ −1(τ=100 μs) / g ⁽²⁾ −1(τ=0.5 μs), where g ⁽²⁾ is the autocorrelation function at the selected angle, τ is the delay time, I is the intensity of the signal, g ^{2(q; τ)} ={I(q,t)I(q,t+τ)}/{I(q,t)} ² , where q is the scattering vector and t is the time, which is the dynamic light scattering It was obtained by measuring a 6.4 wt% polyvinyl alcohol solution with a measuring device (dynamic light scattering, DLS), and the range of the ratio (B) was 0 < (B) < 0.38. Characterized by

In a preferred embodiment, the polyvinyl alcohol further has a block index (η), and the range of block index (η) is 0.4<η<1.

In preferred embodiments, the polyvinyl alcohol further has a 4% aqueous solution clarity (%), wherein the 4% aqueous solution clarity (%) is greater than 98%.

In a preferred embodiment, the polyvinyl alcohol further has a branching index (BI), wherein the branching index (BI)≦0.9.

In a preferred embodiment, the polyvinyl alcohol further has a number average molecular weight (Mn) as analyzed by aqueous phase GPC, wherein the number average molecular weight (Mn)≦12,800.

In a preferred embodiment, polyvinyl alcohol further has a degree of hydrolysis, and the range of degree of hydrolysis is 86-89 mol%.

In a preferred embodiment, the polyvinyl alcohol further has a crystallization temperature (Tc), and the range of the crystallization temperature (Tc) is 135-138°C.

Another object of the present invention is to provide a protective solution, characterized in that it contains polyvinyl alcohol as a dispersant as described above.

Another object of the present invention is to provide a polyvinyl acetate emulsion, characterized in that the polyvinyl acetate emulsion has undergone synthesis with a protective solution as described above.

In a preferred embodiment, the polyvinyl acetate emulsion is left at 60° C. for 2 months, and then subjected to viscosity measurement at room temperature (25° C.). (cp).

The PVA of the present invention is obtained by controlling the alkalinization conditions, block length, and degree of branching, and has a particle size ratio (B) within a specific range. Furthermore, it is possible to obtain a PVA solution of a more stable protective colloid, which has moderate viscosity stability. Therefore, the PVA of the present invention can have good protective colloid effect, can reduce the amount of polyvinyl alcohol used, and has advantageous effects such as relatively stable emulsion viscosity.

The above is not intended to represent all embodiments or all aspects of the present invention, but merely provide examples of the new aspects and features detailed herein. Other features and advantages of the present invention will become readily apparent from the detailed description based on the following drawings. The foregoing drawings illustrate various features of embodiments of the invention by way of example.

It is a conceptual diagram of a measurement state in the dynamic light scattering method. It is a conceptual diagram of the particle size distribution of large particles and small particles in the dynamic light scattering method. It is an autocorrelation function graph of the dynamic light scattering method. 1 is an illustration of the degree of branching of an exemplary PVA of the present invention, (a) is a schematic diagram of branching caused by free radical chain transfer, and (b) is a graph of carbon-13 nuclear magnetic resonance. 1 is a dynamic light scattering graph of exemplary Examples 1-4 and Comparative Examples 1 and 2 according to the present invention, wherein when τ is 100 μs, the y-axes of the Examples are all less than 0.2; All examples are greater than 0.2.

The detailed description and technical contents of the present invention will be described as follows based on the drawings. The proportions in the drawings in the present invention are not drawn to actual proportions for simplicity of explanation, and the drawings and proportions are not intended to limit the scope of the invention. It should be understood that aspects of the invention are not limited to the arrangements, instrumentalities and characteristics shown in the accompanying drawings.

As used herein, unless stated otherwise, the use of "or" means "and/or." As used herein, "comprising" or "comprising" does not exclude the presence of one or more other components, steps, operations and/or components or / or means added to a component. As used herein, "including," "comprising," "containing," "including," and "having" are interchangeable and are not limiting.

As used herein, "one" means one or more (ie, at least one) grammatical object. Similarly, as used in this specification and claims, the singular forms "one", "one", "a" and "the" include plural referents.

Except in the working examples or where otherwise indicated, all numbers indicating amounts of ingredients and/or reaction conditions may be modified in all instances by the term "about" and are indicated in all instances. It means that the value is within ±5% of the figure. As used herein, the terms "essentially free" or "substantially free" mean less than about 2% of the specified property. Any element or feature explicitly recited in this specification may be negatively excluded from a claim.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by one of ordinary skill in the art to which this invention belongs. Also, the following terms used herein have the following meanings.

The present invention relates to polyvinyl alcohol, having a ratio (B), ratio (B)=g ⁽²⁾ −1 (τ=100 μs)/g ⁽²⁾ −1 (τ=0.5 μs) , which was obtained by measuring a 6.4 wt% polyvinyl alcohol solution with a dynamic light scattering measurement device, in which the range of the ratio (B) is about 0 < (B) < 0.38. Characterized by

In another aspect, the invention provides a protective solution, characterized in that it comprises polyvinyl alcohol as described above as a dispersant. In another aspect, the invention provides a polyvinyl acetate emulsion, characterized in that the polyvinyl acetate emulsion has undergone a protective solution synthesis as described above.

As used herein, "dynamic light scattering (DLS)" refers to temporal fluctuation data of scattered light intensity at a specific angle, as shown in FIGS. Particles undergo Brownian motion by colliding with solvent molecules in the solvent, causing fluctuations in the numerical values. g ⁽²⁾ (τ) is the autocorrelation function at the selected angle, τ is the delay time, I is the intensity of the signal, the autocorrelation function has the property of decaying over time, and the stability of the aqueous solution A lower D results in a slower decay rate and a longer decay time. A more stable aqueous solution (less agglomeration) results in a faster decay rate and a shorter decay time. As shown in FIG. 2, the ratio of the numerical value of g ⁽²⁾ -1 in a specific decay time range (τ = 100 μs) to the numerical value of g ⁽²⁾ -1 at the start (τ = 0.5 μs) is It is the ratio (B) in , which is a damping rate index. The smaller the ratio g ⁽²⁾ −1 (τ=100 μs)/g ⁽²⁾ −1 (τ=0.5 μs), the faster the decay rate and the higher the stability of the aqueous solution. After 100 μs, it corresponds to the contribution of particles formed by aggregation of a plurality of PVA molecular chains. In a preferred embodiment, the range of proportion (B) of the PVA of the present invention measured by DLS on a 6.4 wt% polyvinyl alcohol solution is about 0<(B)<0.38. In a preferred embodiment, the ratio (B) of the PVA of the present invention obtained by measuring a 6.4 wt% polyvinyl alcohol solution by DLS is ratio (B)<0.38, such as less than 0.38, 0 less than .37, less than 0.36, less than 0.35, less than 0.34, less than 0.33, less than 0.32, less than 0.31, less than 0.3, less than 0.29, less than 0.28, 0 less than .27, less than 0.26, less than 0.25, less than 0.24, less than 0.23, less than 0.22, less than 0.21, less than 0.2, less than 0.19, less than 0.18, 0 less than .17, less than 0.16, less than 0.15, less than 0.14, less than 0.13, less than 0.12, less than 0.11, less than 0.1, less than 0.09, less than 0.08, 0 but not limited to less than 0.07, less than 0.06, less than 0.05, less than 0.04, less than 0.03, less than 0.02 or less than 0.01. In a preferred embodiment, the range of the ratio (B) of the PVA of the present invention obtained by measuring a 6.4 wt% polyvinyl alcohol solution by DLS is about 0.1 ≤ (B) ≤ 0.3, for example 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0. 23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, or any range between any two values recited above, but is not limited thereto. In a preferred embodiment, the ratio (B) of the PVA of the present invention obtained by measuring a 6.4 wt% polyvinyl alcohol solution by DLS is about 0.11, 0.189, 0.225. , 0.231, 0.254 or 0.298.

The "polyvinyl alcohol (POLYVINYL ALCOHOL, PVA)" used herein is a kind of water-soluble polymer, has good film-forming properties, and the formed film has excellent adhesion, solvent resistance, It has abrasion resistance, tensile strength and oxygen barrier properties. Polyvinyl alcohol has two types of functional groups, a hydrophilic group and a hydrophobic group, at the same time, and is represented by the molecular structure of the following formula (I). It can be used as a protective colloid for emulsion and suspension polymerization reactions.

式（Ｉ）中、Ｏは親水基構造を表し、Ｃは疎水基構造を表している。
ｎは親水基構造のモル数を表し、ｍは疎水基構造のモル数を表している。

In formula (I), O represents a hydrophilic group structure and C represents a hydrophobic group structure.
n represents the number of moles of the hydrophilic group structure, and m represents the number of moles of the hydrophobic group structure.

As used herein, "alkalinization/hydrolysis" is the degree to which a hydrophobic acetic acid group is replaced by a hydrophilic group, and is expressed as n/(n+m). Among them, n and m are respectively the number of moles of hydrophilic group structure and the number of moles of hydrophobic group structure in the PVA molecule, ie n and m in formula (I). The degree of alkalinity is also referred to herein as the degree of hydrolysis, and the higher the value, the higher the affinity for hydrophilic substances. The present inventors discovered that the degree of alkalinity affects the aggregation state of PVA molecular chains in aqueous solution. In preferred embodiments, the range of hydrolysis degree of PVA in the present invention is about 86-89 mol%, such as 86 mol%, 86.1 mol%, 86.2 mol%, 86.3 mol%, 86.4 mol%, 86 mol%. 5mol%, 86.6mol%, 86.7mol%, 86.8mol%, 86.9mol%, 87mol%, 87.1mol%, 87.2mol%, 87.3mol%, 87.4mol%, 87.5mol% , 87.6 mol%, 87.7 mol%, 87.8 mol%, 87.9 mol%, 88 mol%, 88.1 mol%, 88.2 mol%, 88.3 mol%, 88.4 mol%, 88.5 mol%, 88 but not limited to .6 mol %, 88.7 mol %, 88.8 mol %, 88.9 mol %, 89 mol % or any range between any two values recited above. In a preferred embodiment, the range of hydrolysis degree of PVA in the present invention is about 87-88 mol%, such as 87 mol%, 87.1 mol%, 87.15 mol%, 87.2 mol%, 87.25 mol%, 87 mol%. 3 mol%, 87.35 mol%, 87.4 mol%, 87.45 mol%, 87.5 mol%, 87.55 mol%, 87.6 mol%, 87.65 mol%, 87.7 mol%, 87.75 mol%, 87. 8 mol %, 87.85 mol %, 87.9 mol %, 87.95 mol %, 88 mol % or any range between any two values recited above, but not limited thereto. In a more preferred embodiment, the range of hydrolysis degree of PVA in the present invention is 87.09-87.88 mol%, such as 87.09 mol%, 87.17 mol%, 87.58 mol%, 87.81 mol%, 87.81 mol%. 86 mol % or 87.88 mol %, but not limited to these.

As used herein, "blockiness index (η)" refers to the blockiness of the PVA molecule, with higher blockiness resulting in longer crystalline segments. That is, the "O" in the hydrophilic group structure shown in formula (I) becomes longer. NMR is a useful tool for measuring macromolecular microstructure, and the block index (η) used herein is obtained using carbon-13 nuclear magnetic resonance ( ¹³ C NMR). has three prominent resonance peaks in the chemical shift δ=38-46 ppm, VAc-VAc, VOH-VAc, VOH-VOHdiad resonance peaks from right to left, respectively. (VAc, VAc), (VOH, VAc), (VOH, VOH) in the equations below are the area percentages occupied by the resonance peaks at δ=39 ppm, δ=42 ppm and δ=45 ppm, respectively.

式中、Ｉは信号強度である。 Dyad composition:

where I is the signal intensity.

Block exponent (η):

Through the calculation of the block character (η), when 0 ≤ η < 1, it indicates that the polymer has some block characteristics, and when η = 0, the copolymer sample is a block copolymer. (block copolymer), when η = 1, it is a completely random copolymer, and when 1 < η ≤ 2, the sample has a structure of an alternate copolymer. tend to be That is, the lower the η, the higher the blockiness. The inventors discovered that the degree of blocking affects the aggregation state of PVA molecular chains in aqueous solutions. In a preferred embodiment, the block index (η) of the PVA in the present invention is in the range of about 0.4<η<1 to obtain aqueous solution stability, such as 0.4<η≤0.95, 0.4 <η≦0.9, 0.4<η≦0.85, 0.4<η≦0.8, 0.4<η≦0.75, 0.4<η≦0.7, 0.4 <η≦0.65, 0.4<η≦0.6, 0.4<η≦0.55, 0.4<η≦0.5, 0.45≦η<1, 0.5≦η <1, 0.55≤η<1, 0.6≤η<1, 0.65≤η<1, 0.7≤η<1, 0.75≤η<1, 0.8≤η<1 , 0.85≦η<1, 0.9≦η<1, or 0.95≦η<1. When η is less than 0.4, aqueous solution stability is poor, and when η is greater than 1, block polymers and alternating polymers are formed, which are not suitable for controlling aqueous solution stability. In preferred embodiments, the range of block index (η) of PVA in the present invention is about 0.4<η≦0.5, such as 0.401, 0.405, 0.41, 0.415, 0.401, 0.405, 0.41, 0.415, 0.401, 0.405, 0.41, 0.415, 0.401, 0.405, 0.41, 0.415, 0.401, 0.405, 0.41, 0.415, 0.401, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415, 0.415. 42, 0.425, 0.43, 0.435, 0.44, 0.445, 0.45, 0.455, 0.46, 0.465, 0.47, 0.475, 0.48, 0.485, 0.49, 0.495, 0.50 or any range between any two values recited above, but not limited thereto.

As used herein, the "branching index (BI)" is used to describe the degree of branching of the PVA molecular structure, where the free radical chain is C on the OH group (red in FIG. 3(a)). circles) to form branches that cannot be alkalized (blue circles in FIG. 3(a)). The branching index used _herein can be obtained by measurements using ¹³ C NMR, as shown in FIG. It is in between and can be used to quantify the degree of branching, ie, BI=ΣCH/ΣCH ₂ , and if the ratio is too high, the degree of branching will be lower, which is disadvantageous in terms of aqueous solution stability. In preferred embodiments, the branching index of the PVA in the present invention is (BI)≦0.9, such as 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.9. 6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, 0.05 or any of the above A range between, but not limited to, two values. In preferred embodiments, the branching index (BI) of the PVA in the present invention is between 0.7 and 0.9, such as 0.7, 0.71, 0.72, 0.73, 0.74, 0 .75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87 , 0.88, 0.89, 0.9 or any range between any two values recited above, but is not limited thereto.

The polyvinyl alcohol of the present invention has excellent transparency. In preferred embodiments, the transparency (%) in a 4% aqueous solution of polyvinyl alcohol in the present invention is greater than 98%, such as 98.1%, 98.2%, 98.3%, 98.4%, 98.5 %, 98.6%, 98.7%, 98.8%, 98.9%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 100%, but not limited to these.

In a preferred embodiment, the polyvinyl alcohol of the present invention has a number average molecular weight of (Mn)<12815 and is obtained by analysis by aqueous phase GPC. In a preferred embodiment, the polyvinyl alcohol of the present invention has Mn≦12800. In a more preferred embodiment, the Mn of the polyvinyl alcohol of the present invention is between 12600 and 12850, such as 12600, 12610, 12620, 12630, 12640, 12650, 12660, 12670, 12680, 12690, 12700, 12710, 12720, 12730. , 12740, 12750, 12760, 12770, 12780, 12790, 12800, 12810, 12820, 12830, 12840, 12849 or any range between any two values recited above.

In preferred embodiments, the range of crystallization temperature (Tc) of polyvinyl alcohol in the present invention is 135 to 138°C, such as 135°C, 135.1°C, 135.2°C, 135.3°C, 135.4°C. , 135.5°C, 135.6°C, 135.7°C, 135.8°C, 135.9°C, 136°C, 136.1°C, 136.2°C, 136.3°C, 136.4°C, 136 .5°C, 136.6°C, 136.7°C, 136.8°C, 136.9°C, 137°C, 137.1°C, 137.2°C, 137.3°C, 137.4°C, 137.5°C °C, 137.6°C, 137.7°C, 137.8°C, 137.9°C, 138°C, or any range between any two values recited above.

The polyvinyl acetate emulsion of the present invention has good viscosity stability. Or the viscosity change value does not exceed 20,000 (cp). The viscosity change value described above is, for example, 20,000 (cp) or less, 19,000 (cp) or less, 18,000 (cp) or less, 17,000 (cp) or less, 16,000 (cp) or less, 15, 000 (cp) or less, 14,000 (cp) or less, 13,000 (cp) or less, 12,000 (cp) or less, 11,000 (cp) or less, 10,000 (cp) or less, 9,000 ( cp) or less, 8,000 (cp) or less, 7,000 (cp) or less, 6,000 (cp) or less, 5,000 (cp) or less, 4,000 (cp) or less, 3,000 (cp) Below, 2,000 (cp) or less and 1,000 (cp) or less, but not limited to these.

The non-limiting examples of each aspect of the invention provided below are primarily to clarify each aspect of the invention and the effects achieved thereby.

Based on the present invention, PVA was prepared by controlling the degree of alkalinity, degree of blockiness and degree of branching, and it was prepared as PVA aqueous solution Examples 1-6 and Comparative Examples 1-5.

A. Characterization

DLS analysis: The instrument uses Zetasizer Nano ZS, the scattering angle is 173 degrees, PVA RI is 1.479, PVA extinction coefficient is 0, solvent viscosity (water) is 0.8872 cp, solvent refractive index ( water) is 1.33, temperature is 25° C., equilibration time is 0 seconds, disposable cuvettes (type DTS0012) are used for analysis, number of operations is 11, operation time is 10 seconds, number of measurements was 3 times and the delay between measurements was 0 seconds. Three sets of experimental data were measured and averaged.

Preparation of 6.4 wt% PVA aqueous solution: A 6.4 wt% PVA/deionized aqueous solution was prepared in an environment of 70°C, stirred for 12-15 hours, and DLS analysis was performed immediately after the completion of preparation. Filtration using a membrane filter was not performed.

Measurement of crystallization temperature: DSC25 type differential scanning calorimeter (DSC) from TA Instruments was used as the device, and the experimental temperature range was 30°C to 250°C, and the temperature was maintained for 1 minute at each of 30°C and 250°C. The heating/cooling rate was set at 10° C./min, and the crystallization temperature (Tc) at the time of 1 ^st cooling was recorded.

Measurement of block index: The experimental temperature was 27°C, the sample was prepared by dissolving 80 mg of PVA in 1 mL of D ₂ O, and the magnetic field frequency was 500 MHz.

Determination of branching index: The experimental temperature was 27°C, the sample was prepared by dissolving 15 mg of PVA in 1 mL of DMSO, and the magnetic field frequency was 500 MHz.

Measurement of transparency of 4% aqueous solution: The experiment temperature was room temperature, the sample holder of the sample was a quartz cell, the optical path length was 20 mm, and the transparency was measured at 430 nm using a spectrophotometer.

Viscosity Measurements: Viscosity was measured at various shear rates using a Brookfield LVT viscometer with a #4 spindle, measuring at 6 rpm/30 degrees/1 atm followed by increasing shear stress at intervals of less than 1 minute. , for subsequent measurements.

B. Preparation of emulsion

Add 360 g of deionized water into a 2 L reactor, keep the temperature below 30° C., start the agitator, add 52 g of PVA, stir for 15 minutes, and then heat up to 80° C., add PVA Stirring was continued until the was completely dissolved. After the PVA was dissolved, 0.5 g of sodium bicarbonate and 0.5 g of ammonium sulfate were added and completely dissolved. Maintaining the temperature at 80° C., 0.48 g of Ammonium Sulfate was dissolved in 23 g of water and added into the reactor all at once. Thereafter, 495 g of vinyl acetate was added dropwise to the reactor within 6 hours to react. After the above reaction time, 0.24 g of Ammonium
Sulfate was dissolved in 11 g of water, added into the reactor, the reaction temperature was raised to 85° C., and the reaction was continued for 90 minutes. After the reaction was completed, it was cooled to obtain a PVAc emulsion.

C. result

Graphs of the dynamic light scattering method for exemplary Examples 1 to 4 and Comparative Examples 1 and 2 according to the present invention are shown in FIG. See Table 1 for the properties and experimental conditions of Examples 1-6 and Comparative Examples 1-5. Among them, the ratio (B) = g ⁽²⁾ -1 (100) / g ⁽²⁾ -1 (0.5), and in the stability column, O represents uniformity and X represents separation .

Examples 1-6 demonstrate g ⁽²⁾ -1 ratios at specific decay times, specific block lengths and degrees of branching, and whether PVA produces relatively large particle agglomerates in aqueous solutions. It was found that this aggregation is related to block length and branching degree, and that this aggregation also affects emulsion stability and protective colloid properties. Therefore, the present invention can obtain PVA with high protective colloid properties by controlling PVA polymerization and alkalinization conditions.

In comparison, the Comparative Examples tend to form intermolecular aggregates in an aqueous solution state, resulting in a lower decay rate of g ⁽²⁾ −1(τ) and a correspondingly unstable emulsion viscosity. The η-blocking degree is less than 0.4, and the more block, the longer the crystalline segments and the less stable in aqueous solution. The branching index is greater than 0.9, and the lower the degree of branching, the lower the aqueous stability.

In summary, the PVA of the present invention can achieve moderate viscosity stability through moderate alkalinization conditions, moderate block length, and branching degree, and has good protective colloid effect as PVA of protective colloid. , and the use amount of polyvinyl alcohol can be reduced, and it has advantageous effects such as relatively stable emulsion viscosity.

All ranges provided herein are meant to include each particular range within the assigned range and the combination of subranges between the assigned ranges. Also, unless otherwise stated, all ranges provided herein are inclusive of the endpoints of the range, eg between 1 and 5 includes 1 and 5 of both endpoints. Thus, ranges 1-5 specifically include 1, 2, 3, 4 and 5, as well as subranges such as 2-5, 3-5, 2-3, 2-4, 1-4.

All publications and patent applications referred to in this specification are hereby incorporated by reference, and each and every publication or patent application is hereby incorporated by reference for any and all purposes. clearly and individually indicated. In the event of a conflict between this specification and any publication or patent application incorporated herein by reference, the specification shall control.

Claims (10)

Polyvinyl alcohol, said polyvinyl alcohol having a ratio (B), wherein said ratio (B) = g ⁽²⁾ −1 (τ=100 μs)/g ⁽²⁾ −1 (τ=0.5 μs) , which was obtained by measuring a 6.4 wt% polyvinyl alcohol solution with a dynamic light scattering (DLS), wherein the ratio (B) ranged from 0 < (B) Polyvinyl alcohol, characterized in that <0.38. 2. Polyvinyl alcohol according to claim 1, wherein the polyvinyl alcohol further has a block index ([eta]), wherein the range of the block index ([eta]) is 0.4<[eta]<1. 3. The polyvinyl alcohol of claim 1 or claim 2, wherein the polyvinyl alcohol further has a 4% aqueous solution clarity (%), wherein the 4% aqueous solution clarity (%) is greater than 98%. 4. The polyvinyl alcohol according to any one of claims 1 to 3, wherein said polyvinyl alcohol further has a branching index (BI), said branching index (BI) < 0.9. 5. The polyvinyl alcohol of any one of claims 1-4, wherein the polyvinyl alcohol further has a number average molecular weight (Mn), wherein the number average molecular weight (Mn) < 12800. The polyvinyl alcohol according to any one of claims 1 to 5, wherein said polyvinyl alcohol further has a degree of hydrolysis, and said degree of hydrolysis ranges from 86 to 89 mol%. The polyvinyl alcohol according to any one of claims 1 to 6, wherein said polyvinyl alcohol further has a crystallization temperature (Tc), and said crystallization temperature (Tc) ranges from 135 to 138°C. 8. Protective solution, characterized in that it contains the polyvinyl alcohol according to any one of claims 1 to 7 as a dispersant. A polyvinyl acetate emulsion, characterized in that said polyvinyl acetate emulsion has undergone synthesis with the protective solution of claim 8. The polyvinyl acetate according to claim 9, wherein the polyvinyl acetate emulsion essentially does not separate or has a viscosity change value not exceeding 20,000 (cp) after standing at 60°C for 2 months. emulsion.

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