Polyvinyl acetal resin as well as preparation method and application thereof

Abstract

The invention discloses polyvinyl acetal resin as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials, the melt index MI-120 DEG C of the resin at 120 DEG C is less than or equal to 1.50 g / 10min, and the melt index MI-120 DEG C at 120 DEG C and the melt index MI-150 DEG C at 150 DEG C meet the condition that MI-150 DEG C / MI-120 DEG C is more than or equal to 13.50 and less than or equal to 35.0; the problem that a polyvinyl acetal intermediate film is poor in exhaust effect is solved. The preparation method starts from the aspects of molecular weight and distribution regulation, intermolecular chemical cross-linking degree, physical interaction force and the like, and finally realizes regulation of polyvinyl acetal melt index temperature dependence through blending of polyvinyl alcohol raw materials with different polymerization degrees, control of polyvinyl acetal reaction degree and regulation of various parameters. The glass can be applied to laminated safety glass, and has good market competitiveness in the fields of buildings, automobiles, photovoltaics, airplanes and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a polyvinyl acetal resin and a preparation method and application thereof. Background Art

[0002] Polyvinyl acetal resin is widely used in the fields of construction, automobile and photovoltaic safety glass due to its good transparency and chemical stability, excellent film forming property, impact resistance and strong adhesion to glass, metal and other materials. The preparation of laminated safety glass includes: glass cutting, lamination of polyvinyl acetal interlayer and glass, pre-pressing and exhausting, and high-pressure forming. Among them, pre-pressing and exhausting mainly involves pre-pressing and heating in a heating oven by gradually increasing the temperature to remove the air therein, and finally making the glass and the interlayer fuse together, firmly bonded, and almost transparent. This process is crucial to the yield and performance of laminated glass lamination. In addition to the pre-pressing and exhausting parameters, the temperature dependence of the melt index (MI) of the polyvinyl acetal interlayer is the key to determining whether the exhaust is thorough. Because pre-pressing and exhausting are mainly carried out by gradually increasing the temperature, therefore, at low temperatures, if the melt index of the polyvinyl acetal interlayer is too high, the bonding speed between the interlayer and the glass will be faster, resulting in the inability to remove the air in time, which will easily cause bubbles or streaks in uneven places or defects; at high temperatures, if the melt index of the polyvinyl acetal interlayer is too low, it will be difficult to achieve a close fit between the interlayer and the glass. Therefore, in the preparation of laminated safety glass, the polyvinyl acetal interlayer is required to have a good temperature dependence of the melt index, that is, the product melt index is low at low temperatures and high at high temperatures. However, current conventional resin products show the characteristics of a high low-temperature melt index and a low high-temperature melt index, which to a certain extent leads to the inability of polyvinyl acetal interlayer products to be stably used in laminated safety glass, especially polyvinyl acetal interlayer used in automotive laminated safety glass.

[0003] The melt index of polyvinyl acetal is closely related to its molecular weight and its distribution, the degree of chemical crosslinking and physical interaction between molecules. At low temperatures, the chemical crosslinking and physical interaction between molecules are difficult to be destroyed, so polyvinyl acetal shows a lower melt index performance at low temperatures. As the temperature rises, the degree of chemical crosslinking between molecules does not change, so it will not affect the melt index of the product at high temperatures; however, the material activity of the low molecular weight structure in polyvinyl acetal is enhanced, and its fluidity is significantly improved, which to a certain extent improves the melt index of the product at high temperatures; in addition, as the temperature rises, the physical interaction between molecules represented by hydrogen bond interactions is gradually destroyed, which to a certain extent can further improve the melt index performance of the product at high temperatures.

[0004] The patent with application number 202111098317.X adopts the method of mixing high-polymerization degree and low-polymerization degree polyvinyl alcohol first and then acetalizing to prepare a PVB resin product with a melt index of 0.90-1.10g / 10min at 118°C, but it does not characterize the melt index performance of the corresponding resin product at high temperature, and cannot effectively evaluate the temperature dependence of the melt index of its product; in addition, the characterization of the melt index of the resin product is only 25wt%. If the plasticizer content is further increased, its melt index at low temperature may be further improved. The patent application with publication number CN117362490A mentions starting from the aggregated structure of polyvinyl alcohol, controlling the crystallization behavior of polyvinyl alcohol, introducing inorganic salt ions, and optimizing the feeding process. The melt index at high temperature is then regulated by increasing the insulation temperature, extending the insulation time, etc., and finally realizing the regulation of the temperature dependence of the melt index of polyvinyl alcohol acetal. This method may help to regulate the temperature dependence of the melt index of polyvinyl acetal to a certain extent, but overall, this regulation method has high requirements on the polyvinyl alcohol raw materials, relatively complex process parameters and the addition of a large amount of inorganic salts, which not only increases the production cost, but also easily causes water washing difficulties. The residual trace ions will have an adverse effect on the weather resistance and aging resistance of the product. Summary of the invention

[0005] The purpose of the present invention is to provide a polyvinyl acetal resin to solve the problem of poor exhaust effect of polyvinyl acetal interlayer; to provide a method for preparing polyvinyl acetal resin to solve the problem of poor temperature dependence of the melt index of polyvinyl acetal resin; to provide an application of polyvinyl acetal resin in laminated glass to solve the problem that existing products are difficult to use stably in laminated glass.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a polyvinyl acetal, wherein the melt index MI-120℃ at 120℃≤1.50g / 10min, and the melt index MI-120℃ at 120℃ and the melt index MI-150℃ at 150℃ satisfy: 13.50≤MI-150℃ / MI-120℃≤35.00.

[0008] As a further preferred embodiment of the present invention, the hydroxyl value of the polyvinyl acetal resin is 9.00-19.00 wt %.

[0009] As a further preferred embodiment of the present invention, the polyvinyl acetal corresponds to a polyvinyl acetal intermediate film with a tensile strength of more than 24.0 MPa, a light transmittance of more than 90.0%, no bubbles and no color in a heat resistance test; and the corresponding laminated safety glass has no bubbles and no streaks.

[0010] In a second aspect, the present invention provides a method for preparing a polyvinyl acetal resin, comprising the following steps:

[0011] Polyvinyl alcohols with different polymerization degrees are partially hydroformylated respectively, and the partially hydroformylated ones are mixed for final hydroformylation, and an alkali solution is added to terminate the reaction to obtain a polyvinyl alcohol acetal resin.

[0012] As a further preferred embodiment of the present invention, the partial hydroformylation comprises the following steps:

[0013] a. Add polyvinyl alcohol A to pure water, heat and stir to dissolve, and cool to the condensation reaction temperature to obtain polyvinyl alcohol A reaction solution; add polyvinyl alcohol B to pure water, heat and stir to dissolve, and cool to the condensation reaction temperature to obtain polyvinyl alcohol B reaction solution;

[0014] b. Add part of hydrochloric acid and part of n-butyraldehyde to the polyvinyl alcohol A reaction stock solution and the polyvinyl alcohol B reaction stock solution respectively, and stir the reaction for 0.5 to 2 hours to obtain polyvinyl acetal solution A and polyvinyl acetal solution B with different hydroxyl values ​​and homogeneous phase; then, mix the polyvinyl acetal solution A and the polyvinyl acetal solution B to obtain polyvinyl acetal solution C, and stir and disperse the polyvinyl acetal solution C.

[0015] As a further preferred embodiment of the present invention, the final hydroformylation comprises the following steps:

[0016] Add the remaining n-butyraldehyde to the polyvinyl acetal solution C, control the ratio of the total amount of n-butyraldehyde added to the total mass of polyvinyl alcohol A and B in the reaction system to be 0.58-0.70, then raise the temperature to 65-75° C. at 25° C. / h and stir the reaction for 1-4 hours to obtain a polyvinyl acetal slurry.

[0017] As a further preferred embodiment of the present invention, adding alkali solution to terminate the reaction comprises the following steps:

[0018] The obtained polyvinyl acetal slurry is cooled to 20-40° C., and a sodium hydroxide solution is added to terminate the reaction to obtain a suspension containing polyvinyl acetal resin;

[0019] The polyvinyl acetal resin suspension is repeatedly washed with water and the pH value of the solution is controlled to be between 7 and 8. The suspension is centrifuged and dried to obtain the polyvinyl acetal resin.

[0020] As a further preferred embodiment of the present invention, the prepared polyvinyl acetal resin has a hydroxyl value of 9.00-19.00 wt%, MI-120°C ≤ 1.50 g / 10 min, and a melt index MI-120°C at 120°C and a melt index MI-150°C at 150°C satisfying: 13.50≤MI-150°C / MI-120°C≤35.00.

[0021] As a further preferred embodiment of the present invention, in step a, the degree of polymerization of the polyvinyl alcohol A is between 1500 and 2600, and the degree of polymerization of the polyvinyl alcohol B is between 250 and 1200; the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B satisfies 5.7≤mA / mB≤65.7; the blending of polyvinyl alcohol raw materials with different polymerization degrees is the key to regulating the molecular weight and distribution, and is the basis for realizing the temperature dependence of the melt index of the polyvinyl alcohol acetal resin; but with the introduction of low-polymerization degree polyvinyl alcohol raw materials, the molecular weight of the synthesized polyvinyl alcohol acetal resin is relatively low, which will have a greater impact on the melt index performance. If the proportion of low-polymerization degree polyvinyl alcohol raw materials introduced exceeds a certain range, it will not help to improve the temperature dependence of the melt index. In addition, with the introduction of low molecular weight substances, it is easy to cause problems such as bubbles or coloring during resin processing and service, so the proportion of low-polymerization degree polyvinyl alcohol must be strictly controlled.

[0022] As a further preferred embodiment of the present invention, in step a, the alcoholysis degree of the polyvinyl alcohols A and B is between 88% and 99%.

[0023] As a further preferred embodiment of the present invention, in step a, the theoretical degree of polymerization of the polyvinyl alcohol A and the polyvinyl alcohol B blended is 1700-2000.

[0024] As a further preferred embodiment of the present invention, in step a, the condensation reaction temperature of the polyvinyl alcohol A reaction stock solution is above 16°C; the condensation reaction temperature of the polyvinyl alcohol B reaction stock solution is 0-12°C; the condensation reaction temperature is an important means to control the uniformity of the reaction, regulate the distribution of hydroxyl groups, and then regulate the hydrogen bond interaction between molecules; in the polyvinyl alcohol A reaction stock solution with a high degree of polymerization, it has a strong tolerance to temperature, and the distribution ratio of continuous hydroxyl groups can be increased by a higher low-temperature condensation temperature, thereby increasing the hydrogen bond interaction between molecules, so that the polyvinyl alcohol acetal resin exhibits low melt index performance at low temperatures because the hydrogen bond interaction is difficult to be destroyed, and exhibits high melt index performance at high temperatures because the hydrogen bond interaction is destroyed. In the polyvinyl alcohol B reaction stock solution with a low degree of polymerization, because it has a poor tolerance to temperature, the reaction temperature needs to be strictly controlled to prevent agglomeration.

[0025] As a further preferred embodiment of the present invention, in step b, 20% to 30% of hydrochloric acid solution relative to the mass of polyvinyl alcohol A is added to the polyvinyl alcohol A reaction stock solution, and then 8.0% to 20.0% of n-butyraldehyde relative to the mass of polyvinyl alcohol A is added within 10 to 30 minutes to obtain a homogeneous polyvinyl acetal solution A;

[0026] In step b, a hydrochloric acid solution of 5% to 15% by weight of the polyvinyl alcohol B is added to the polyvinyl alcohol B reaction stock solution, and then 2.5% to 6.0% by weight of n-butyraldehyde is added within 10 to 30 minutes to obtain a homogeneous polyvinyl acetal solution B;

[0027] As a further preferred solution of the present invention, in step b, the difference in hydroxyl values ​​between the polyvinyl acetal solutions A and B is in the range of 10.00-20.00wt%, that is, the hydroxyl value content of the polyvinyl acetal solution A is lower than that of the polyvinyl acetal solution B; the hydroxyl value content is a key indicator reflecting the degree of acetalization of the resin, and is also the key to regulating the hydrogen bond interaction between molecules. Since the final product polyvinyl acetal resin is used in the field of intermediate films, there are strict requirements on the hydroxyl value of the product, and it is impossible to achieve the regulation of hydrogen bond interaction by increasing the hydroxyl value content of the final product. Therefore, by regulating the difference in the degree of reaction of polyvinyl alcohol raw materials with different polymerization degrees, a resin blend with high acetal degree (low hydroxyl value) and low acetal degree (high hydroxyl value) is formed in the molecular structure, thereby ensuring the hydroxyl value of the final resin product while forming a strong hydrogen bond interaction between its molecules.

[0028] As a further preferred embodiment of the present invention, in step b, the stirring time of the polyvinyl acetal solution C is more than 30 minutes; the stirring time determines the uniformity of the polyvinyl acetal solution C, and thus also determines the uniformity of the distribution of molecular chains of different sizes and hydrogen bonds; if the stirring time is too short, it will lead to uneven distribution of molecular chains of different sizes and hydrogen bonds, and ultimately the temperature dependence of the melt index of the product cannot be achieved.

[0029] In a third aspect, the present invention provides an application of polyvinyl acetal resin in laminated safety glass. The laminated safety glass is applied in the fields of architecture, automobile, photovoltaic and aircraft, such as architectural sound insulation glass, automobile laminated glass, solar photovoltaic laminated glass and laminated safety glass.

[0030] Beneficial effects of the present invention:

[0031] The present invention starts from the perspectives of regulating molecular weight and distribution, the degree of chemical crosslinking and physical interaction between molecules, and ultimately achieves the regulation of the temperature dependence of the melt index of polyvinyl acetal by blending polyvinyl alcohol raw materials with different polymerization degrees, controlling the degree of polyvinyl acetal reaction and regulating various parameters.

[0032] According to the present invention, the temperature dependence of the melt index of polyvinyl acetal can be controlled by only designing polyvinyl alcohol raw materials with different polymerization degrees and controlling process parameters without adding ionic salts.

[0033] The process of the invention is simple, and compared with the existing production process, no emulsifier or other additives that may affect product performance need to be added during the reaction process of the invention, and the invention has good market competitiveness. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example A1

[0036] 1) In a No. 1 reactor, 43.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 and a degree of alcoholysis of 99% was dissolved in 43.5 L of pure water, stirred at 100° C. for 3 hours to fully dissolve it, and then cooled to 20° C. to obtain a polyvinyl alcohol A reaction stock solution; in a No. 2 reactor, 6.5 kg of polyvinyl alcohol with an average degree of polymerization of 460 and a degree of alcoholysis of 99% was dissolved in 6.5 L of pure water, stirred at 90° C. for 3 hours to fully dissolve it, and then cooled to 5° C. to obtain a polyvinyl alcohol B reaction stock solution; the theoretical degree of polymerization after mixing polyvinyl alcohol A and B was controlled to be 1700;

[0037] 2) Within 15 minutes, add 10.875 kg of 33% hydrochloric acid solution to the polyvinyl alcohol A reaction stock solution in the 1# reactor, then add 3.7845 kg of n-butyraldehyde within 30 minutes, and stir and react for 30 minutes to obtain polyvinyl alcohol acetal solution A; at the same time, within 15 minutes, add 0.65 kg of 33% hydrochloric acid solution to the polyvinyl alcohol B reaction stock solution in the 2# reactor, then add 0.1885 kg of n-butyraldehyde within 30 minutes, and stir and react for 30 minutes to obtain polyvinyl alcohol acetal solution B. The polyvinyl alcohol acetal solutions A and B in the 1# and 2# reactors are poured into the 3# reactor to obtain polyvinyl alcohol acetal solution C, and the polyvinyl alcohol acetal solution C is stirred for 40 minutes;

[0038] 3) Add 25.027 kg of n-butyraldehyde to the polyvinyl acetal solution C within 30 minutes; after the addition of the raw materials, keep the temperature at this temperature for 15 minutes, then increase the temperature to 65° C. at a rate of 25° C. / h and stir for 2 hours to obtain a polyvinyl acetal slurry;

[0039] 3) cooling the obtained polyvinyl acetal slurry to 30° C., adding a sodium hydroxide solution to terminate the reaction, and obtaining a suspension containing polyvinyl acetal resin;

[0040] 4) The polyvinyl acetal resin suspension is repeatedly washed with water at 55° C. for 10 times and the pH value of the solution is controlled at 7-8. The suspension is centrifuged and then dried in a forced air drying oven at 55° C. for 12 hours to obtain the polyvinyl acetal resin product.

[0041] Example A2

[0042] (Compared with Example A1, the ratio of polyvinyl alcohol B is reduced, the degree of polymerization of polyvinyl alcohol A is reduced - the ratio is increased)

[0043] Except for step 1), in the 1# reactor, 43.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 is replaced by 46.5 kg of polyvinyl alcohol with an average degree of polymerization of 1770; in the 2# reactor, 6.5 kg of polyvinyl alcohol with an average degree of polymerization of 460 is replaced by 3.5 kg of polyvinyl alcohol with an average degree of polymerization of 460; in steps 2) and 3), the corresponding hydrochloric acid and butyraldehyde added to the polyvinyl alcohol A reaction stock solution, polyvinyl alcohol B reaction stock solution, and polyvinyl alcohol acetal solution C are increased or decreased in proportion to the change in the mass of polyvinyl alcohol, and the remaining steps and conditions are the same as Example A1.

[0044] Example A3

[0045] (Compared with Example A1, polyvinyl alcohol A was changed to blended polyvinyl alcohol)

[0046] Except that in step 1), in reactor #1, 43.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 is replaced by a mixture of 26.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 and 20.0 kg of polyvinyl alcohol with an average degree of polymerization of 1650, and the corresponding hydrochloric acid and butyraldehyde in steps 2) and 3) are increased or decreased in proportion, the remaining steps and conditions are the same as those in Example A1.

[0047] Example A4

[0048] (Compared with Example A1, the degree of polymerization of polyvinyl alcohol A is increased and the degree of polymerization of polyvinyl alcohol B is decreased)

[0049] Except for step 1) the polyvinyl alcohol with an average degree of polymerization of 1860 in reactor #1 was replaced with polyvinyl alcohol with a degree of polymerization of 1900, and the polyvinyl alcohol with an average degree of polymerization of 460 in reactor #2 was replaced with polyvinyl alcohol with a degree of polymerization of 200, the remaining steps and conditions were the same as those in Example A1.

[0050] Example A5

[0051] (Compared with Example A1, the acetalization temperature of the polyvinyl alcohol A reaction stock solution is lowered)

[0052] Except that the temperature of the 1# reactor in step 1) is changed from 20°C to 16°C, that is, the acetalization temperature of the polyvinyl alcohol A reaction stock solution is changed from 20°C to 16°C, the remaining steps and conditions are the same as those in Example A1.

[0053] Example A6

[0054] (Compared with Example A1, the acetalization temperature of the polyvinyl alcohol A reaction stock solution is increased)

[0055] Except that the temperature of the 1# reactor in step 1) is changed from 20°C to 25°C, that is, the acetalization temperature of the polyvinyl alcohol A reaction stock solution is changed from 20°C to 25°C, the remaining steps and conditions are the same as those in Example A1.

[0056] Example A7

[0057] (Compared with Example A1, the acetalization temperature of the polyvinyl alcohol A reaction stock solution is increased)

[0058] Except that the temperature of the 1# reactor in step 1) is changed from 20°C to 30°C, that is, the acetalization temperature of the polyvinyl alcohol A reaction stock solution is changed from 20°C to 30°C, the remaining steps and conditions are the same as those in Example A1.

[0059] Example A8

[0060] (Compared with Example A1, the acetalization temperature of the polyvinyl alcohol B reaction stock solution is lowered)

[0061] Except that the temperature of the 2# reactor in step 1) is changed from 5°C to 0°C, that is, the acetalization temperature of the polyvinyl alcohol B reaction stock solution is changed from 5°C to 0°C, the remaining steps and conditions are the same as those in Example A1.

[0062] Embodiment A9

[0063] (Compared with Example A1, the acetalization temperature of the polyvinyl alcohol B reaction stock solution is increased)

[0064] Except that the temperature of the 2# reactor in step 1) is changed from 5°C to 10°C, that is, the acetalization temperature of the polyvinyl alcohol B reaction stock solution is changed from 5°C to 10°C, the remaining steps and conditions are the same as those in Example A1.

[0065] Embodiment A10

[0066] (Compared with Example A1, the acetalization temperature of the polyvinyl alcohol B reaction stock solution is increased)

[0067] Except that the temperature of the 2# reactor in step 1) is changed from 5°C to 12°C, that is, the acetalization temperature of the polyvinyl alcohol B reaction stock solution is changed from 5°C to 12°C, the remaining steps and conditions are the same as those in Example A1.

[0068] Embodiment A11

[0069] (Compared with Example A1, the stirring time of the polyvinyl acetal solution C was increased)

[0070] Except that the stirring time of the obtained polyvinyl acetal solution C is increased from 40 min to 60 min in step 2), the remaining steps and conditions are the same as those in Example A1.

[0071] Example A12

[0072] (Compared with Example A1, the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is controlled at 5.7)

[0073] Except that in step 1), in reactor #1, 43.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 is replaced with 37.05 kg of polyvinyl alcohol with an average degree of polymerization of 1860, and the corresponding hydrochloric acid and butyraldehyde in steps 2) and 3) are increased or decreased in proportion, the remaining steps and conditions are the same as those in Example A1.

[0074] Embodiment A13

[0075] (Compared with Example A1, the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is controlled at 65.7)

[0076] Except that in step 1), in reactor #1, 43.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 is replaced with 427.05 kg of polyvinyl alcohol with an average degree of polymerization of 1860, and the corresponding hydrochloric acid and butyraldehyde in steps 2) and 3) are increased or decreased in proportion, the remaining steps and conditions are the same as those in Example A1.

[0077] Embodiment A14

[0078] (Compared with Example A1, hydrogen bond interaction was regulated and MI-150℃ / MI-120℃ was controlled at 35)

[0079] Except that in step 1), the temperature of reactor #1 was changed from 20°C to 30°C, that is, the acetalization temperature of the reaction stock solution of polyvinyl alcohol A was changed from 20°C to 30°C; the temperature of reactor #2 was changed from 5°C to 12°C, that is, the acetalization temperature of the reaction stock solution of polyvinyl alcohol B was changed from 5°C to 12°C; except that in step 3), 25.0270 kg of n-butyraldehyde was added to the polyvinyl alcohol acetal solution C within 30 min instead of adding 30.0270 kg of n-butyraldehyde, the remaining steps and conditions were the same as those in Example A1.

[0080] Embodiment A15

[0081] (The alcoholysis degree of polyvinyl alcohol A and B was changed from 99% to 88%)

[0082] Except that the alcoholysis degree of polyvinyl alcohol A and B in step 1) was changed from 99% to 88%, the remaining steps and conditions were the same as those in Example A1.

[0083] Embodiment A16

[0084] (Compared with Example A1, the alcoholysis degree of polyvinyl alcohol A and B was changed from 99% to 92%)

[0085] Except that the alcoholysis degree of polyvinyl alcohol A and B in step 1) was changed from 99% to 92%, the remaining steps and conditions were the same as those in Example A1.

[0086] Embodiment A17

[0087] (Compared with Example A1, the theoretical degree of polymerization after mixing polyvinyl alcohol A and B is controlled to 2000)

[0088] Except that in step 1), the polyvinyl alcohol with an average degree of polymerization of 1860 and a degree of alcoholysis of 99% is replaced with polyvinyl alcohol with an average degree of polymerization of 2250 and a degree of alcoholysis of 99%, and the theoretical degree of polymerization after mixing polyvinyl alcohol A and B is controlled to be around 2000, the remaining steps and conditions are the same as those in Example A1.

[0089] Comparative Example A1

[0090] (Compared with Example A1, polyvinyl alcohol blending with the same degree of polymerization was implemented)

[0091] Except for step 1) replacing the polyvinyl alcohol with an average degree of polymerization of 1860 in the 1# reactor with polyvinyl alcohol with an average degree of polymerization of 1700; and replacing the polyvinyl alcohol with an average degree of polymerization of 460 in the 2# reactor with polyvinyl alcohol with an average degree of polymerization of 1700, the remaining steps and conditions are the same as those in Example A1.

[0092] Comparative Example A2

[0093] (Compared with Example A1, the hydrogen bonding interaction was not regulated - the acetalization temperature of the polyvinyl alcohol A reaction stock solution was lowered)

[0094] Except that the temperature of the 1# reactor in step 1) is changed from 20°C to 15°C, that is, the acetalization temperature of the polyvinyl alcohol A reaction stock solution is changed from 20°C to 15°C, the remaining steps and conditions are the same as those in Example A1.

[0095] Comparative Example A3

[0096] (Compared with Example A1, the difference in hydroxyl values ​​between polyvinyl acetal solutions A and B was not regulated)

[0097] Except that in step 2), 0.1885 kg of n-butyraldehyde is added to the polyvinyl alcohol B reaction stock solution in the 2# reactor instead of 0.4000 kg, the remaining steps and conditions are the same as those in Example A1.

[0098] Comparative Example A4

[0099] (Compared with Example A1, the stirring time of the polyvinyl acetal solution C was reduced)

[0100] Except that the stirring time of the obtained polyvinyl acetal solution C is increased from 40 min to 30 min in step 2), the remaining steps and conditions are the same as those in Example A1.

[0101] Comparative Example A5

[0102] (Compared with Example A1, the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is controlled at 5.6)

[0103] Except that in step 1), in reactor #1, 43.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 is replaced with 36.40 kg of polyvinyl alcohol with an average degree of polymerization of 1860, and the corresponding hydrochloric acid and butyraldehyde in steps 2) and 3) are increased or decreased in proportion, the remaining steps and conditions are the same as those in Example A1.

[0104] Comparative Example A6

[0105] (Compared with Example A1, the mass ratio of polyvinyl alcohol A to polyvinyl alcohol B is controlled at 65.8)

[0106] Except that in step 1), in reactor #1, 43.5 kg of polyvinyl alcohol with an average degree of polymerization of 1860 is replaced with 427.70 kg of polyvinyl alcohol with an average degree of polymerization of 1860, and the corresponding hydrochloric acid and butyraldehyde in steps 2) and 3) are increased or decreased in proportion, the remaining steps and conditions are the same as those in Example A1.

[0107] Comparative Example A7

[0108] (Compared with Example A1, two polyvinyl acetal products synthesized from polyvinyl alcohol with different polymerization degrees were mixed)

[0109] In addition to adding corresponding butyraldehyde and hydrochloric acid raw materials to the polyvinyl alcohol A reaction stock solution in the 1# reactor and the polyvinyl alcohol B reaction stock solution in the 2# reactor in step 2), the reactions are carried out separately without premixing the reaction; after the corresponding polyvinyl alcohol acetal resins prepared from polyvinyl alcohols with different polymerization degrees are obtained respectively, the finished polyvinyl alcohol acetal resins are mixed.

[0110] The hydroxyl values ​​of polyvinyl alcohol A and polyvinyl alcohol B in Examples A1 to A17 and Comparative Examples A1 to A7 are shown in Table 1:

[0111] Table 1

[0112]

[0113] The hydroxyl values, MI-120°C and MI-150°C of the polyvinyl acetal resins prepared in Examples A1 to A17 and Comparative Examples A1 to A7 are shown in Table 2:

[0114] Table 2

[0115]

[0116]

[0117] Application Example A1

[0118] 50 kg of the polyvinyl acetal resin prepared in Example A1 and 18.97 kg of a plasticizer (triethylene glycol di-2-ethylhexanoate) were taken and plasticized and extruded through an extruder to prepare a polyvinyl acetal intermediate film. The extruder screw speed was 220 r / min; the temperatures of each zone of the extruder were 40°C, 70°C, 150°C, 150°C, 150°C, 150°C, 140°C, and 120°C respectively; the thickness of the polyvinyl acetal intermediate film prepared was 0.76 mm.

[0119] The intermediate film obtained above was cut into a size of 300mm*300mm and stored at 23℃ for 10 hours. The intermediate film was inserted between two transparent glasses (300mm*300mm) to obtain a laminate. The outer periphery of the laminate was sealed with a width of 2cm from the end by heat welding, and the laminate was gradually heated from 23℃ to 120℃ within 2h and kept warm for 30min; then the temperature was raised to 150℃ and the pressure was controlled at 1.3MPa, and pressed for 20 minutes to obtain the corresponding laminated safety glass.

[0120] Application Examples A2-A17

[0121] Except that the polyvinyl acetal resin in Application Example A1 is replaced by the polyvinyl acetal resin prepared in Examples A2-A15, the remaining steps and conditions are the same as those in Application Example A1.

[0122] Comparative Application Examples A1-A7

[0123] Except that the polyvinyl acetal resin in Application Example A1 is replaced by the polyvinyl acetal resin prepared in Comparative Examples A1-A7, the remaining steps and conditions are the same as those in Application Example A1.

[0124] The polyvinyl acetal intermediate films and laminated safety glasses prepared by Application Example A1 to Application Example A17 and Application Comparative Example A1 to Application Comparative Example A7 are shown in Table 3:

[0125] Table 3

[0126]

[0127] The hydroxyl value of the polyvinyl acetal resin prepared above is tested by chemical titration. The hydroxyl groups in the polyvinyl acetal resin are esterified with acetic anhydride in a pyridine solution, and then the excess acetic anhydride is hydrolyzed. Phenolphthalein is used as an indicator, and the hydroxyl content in the polyvinyl acetal resin is calculated by titration and neutralization with a NaOH standard solution.

[0128] The testing method for the melt index of the polyvinyl acetal resin prepared above at 120°C and 150°C is as follows: take a certain amount of polyvinyl acetal resin and plasticizer triethylene glycol diisooctanoate, control the proportion of plasticizer in the total amount to 27.5wt%, pass through a melt index meter at 120°C, 150°C, and a load of 21.6kg, and record the outflow mass after 10 minutes as its melt index, in units of g / 10min.

[0129] The tensile strength of the polyvinyl acetal intermediate film prepared above is tested according to the national standard GB / T32020-2012.

[0130] The test method for the light transmittance of the polyvinyl acetal intermediate film prepared above is: according to the national standard GB / T32020-2012.

[0131] The test method for the heat resistance test of the polyvinyl acetal intermediate film prepared above is: according to the national standard GB / T5137.3-2020.

[0132] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0133] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyvinyl acetal, characterized in that The melt index MI-120℃ at 120℃≤1.50g / 10min, and the melt index MI-120℃ at 120℃ and the melt index MI-150℃ at 150℃ satisfy: 13.50≤MI-150℃ / MI-120℃≤35.

00.

2. A polyvinyl acetal according to claim 1, characterized in that: The hydroxyl value of the polyvinyl acetal resin is 9.00-19.00 wt %.

3. A polyvinyl acetal according to claim 1, characterized in that: The polyvinyl acetal corresponds to a polyvinyl acetal intermediate film with a tensile strength of more than 24.0 MPa, a light transmittance of more than 90.0%, no bubbles and no color in a heat resistance test; and corresponds to a laminated safety glass with no bubbles and no streaks.

4. A method for preparing a polyvinyl acetal resin, characterized in that: The following steps are involved: Polyvinyl alcohols with different polymerization degrees are partially hydroformylated respectively, and the partially hydroformylated ones are mixed for final hydroformylation, and an alkali solution is added to terminate the reaction to obtain a polyvinyl alcohol acetal resin.

5. The method for preparing a polyvinyl acetal resin according to claim 4, characterized in that: Partial hydroformylation includes the following steps: a. Add polyvinyl alcohol A to pure water, heat and stir to dissolve, and cool to the condensation reaction temperature to obtain polyvinyl alcohol A reaction solution; add polyvinyl alcohol B to pure water, heat and stir to dissolve, and cool to the condensation reaction temperature to obtain polyvinyl alcohol B reaction solution; b. Add part of hydrochloric acid and part of n-butyraldehyde to the polyvinyl alcohol A reaction stock solution and the polyvinyl alcohol B reaction stock solution respectively, and stir the reaction for 0.5 to 2 hours to obtain polyvinyl acetal solution A and polyvinyl acetal solution B with different hydroxyl values ​​and homogeneous phase; then, mix the polyvinyl acetal solution A and the polyvinyl acetal solution B to obtain polyvinyl acetal solution C, and stir and disperse the polyvinyl acetal solution C.

6. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: The final hydroformylation process includes the following steps: Add the remaining n-butyraldehyde to the polyvinyl acetal solution C, control the ratio of the total amount of n-butyraldehyde added to the total mass of polyvinyl alcohol A and B in the reaction system to be 0.58-0.70, then raise the temperature to 65-75° C. at 25° C. / h and stir the reaction for 1-4 hours to obtain a polyvinyl acetal slurry.

7. The method for preparing a polyvinyl acetal resin according to claim 4, characterized in that: Adding alkali solution to terminate the reaction comprises the following steps: The obtained polyvinyl acetal slurry is cooled to 20-40° C., and a sodium hydroxide solution is added to terminate the reaction to obtain a suspension containing polyvinyl acetal resin; The polyvinyl acetal resin suspension is repeatedly washed with water and the pH value of the solution is controlled to be between 7 and 8. The suspension is centrifuged and dried to obtain the polyvinyl acetal resin.

8. The method for preparing a polyvinyl acetal resin according to claim 4, characterized in that: The prepared polyvinyl acetal resin has a hydroxyl value of 9.00-19.00 wt%, MI-120°C≤1.50 g / 10 min, and a melt index MI-120°C at 120°C and a melt index MI-150°C at 150°C satisfying: 13.50≤MI-150°C / MI-120°C≤35.

00.

9. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: In step a, the degree of polymerization of the polyvinyl alcohol A is between 1500 and 2600, and the degree of polymerization of the polyvinyl alcohol B is between 250 and 1200; the mass ratio of the polyvinyl alcohol A to the polyvinyl alcohol B satisfies 5.7≤mA / mB≤65.

7.

10. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: In step a, the alcoholysis degree of the polyvinyl alcohol A and the polyvinyl alcohol B is 88% to 99%.

11. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: In step a, the theoretical degree of polymerization of the polyvinyl alcohol A and the polyvinyl alcohol B blended is 1700-2000.

12. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: In step a, the condensation reaction temperature of the polyvinyl alcohol A reaction stock solution is above 16°C; the condensation reaction temperature of the polyvinyl alcohol B reaction stock solution is between 0 and 12°C.

13. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: In step b, a hydrochloric acid solution of 20% to 30% by weight of the polyvinyl alcohol A is added to the polyvinyl alcohol A reaction stock solution, and then 8.0% to 20.0% by weight of n-butyraldehyde is added within 10 to 30 minutes to obtain a homogeneous polyvinyl acetal solution A; In step b, 5% to 15% hydrochloric acid solution is added to the polyvinyl alcohol B reaction stock solution, and then 2.5% to 6.0% n-butyraldehyde is added within 10 to 30 minutes to obtain a homogeneous polyvinyl acetal solution B.

14. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: In step b, the difference in hydroxyl value between the polyvinyl acetal solution A and the polyvinyl acetal solution B is in the range of 10.00-20.00 wt %, that is, the hydroxyl value content of the polyvinyl acetal solution A is lower than that of the polyvinyl acetal solution B.

15. The method for preparing a polyvinyl acetal resin according to claim 5, characterized in that: In step b, the stirring time of the polyvinyl acetal solution C is more than 30 minutes.

16. Use of the polyvinyl acetal resin according to any one of claims 1 to 3 or the polyvinyl acetal resin prepared by the preparation method according to any one of claims 4 to 15 in laminated safety glass.

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