Polymer films and their applications

Abstract

The present invention provides a polymer film, which includes a first layer, a second layer, and a third layer in sequence, wherein two surfaces of the second layer are in contact with the first layer and the third layer respectively, the first layer has a first melt index, the second layer has a second melt index, and the third layer has a third melt index, wherein the second melt index is 3.5 g / 10 minutes to 10.0 g / 10 minutes, the first melt index and the third melt index are each independently less than 3.5 g / 10 minutes, and the difference between the second melt index and the first melt index and the difference between the second melt index and the third melt index are each independently 0.2 g / 10 minutes to 8.5 g / 10 minutes.

Description

Technical Field

[0001] The present invention relates to a polymer film, and more particularly to a multilayer polymer film having a specific melt index (MI) characteristic. The present invention also relates to a laminated glass prepared using the polymer film. Background Art

[0002] Laminated glass is a composite glass material made by sandwiching a polymer film between two sheets of glass. The glass sheets and the polymer film are tightly bonded together through heat pressing. Laminated glass is widely used in the automotive and construction industries due to its excellent impact resistance and safety.

[0003] Polymer films used in laminated glass can have a multilayer structure to provide laminated glass with desired functionality. For example, a polymer film comprising two outer layers and a sound-insulating interlayer positioned between the two outer layers can be used to produce laminated glass with sound insulation. Generally speaking, polymer films used in laminated glass with sound insulation must have a certain thickness of the interlayer and a uniform overall structure to provide good sound damping and achieve the desired sound insulation performance. Summary of the Invention

[0004] The present invention aims to provide a polymer film having a multilayer structure. By combining materials with specific melt indexes, the provided polymer film has good structural uniformity and can produce laminated glass with excellent sound insulation and no optical defects. Therefore, the polymer film is particularly suitable for the preparation of soundproof laminated glass.

[0005] Therefore, one object of the present invention is to provide a polymer film, which comprises a first layer, a second layer and a third layer in sequence, and the two surfaces of the second layer are in contact with the first layer and the third layer respectively, the first layer has a first melt index, the second layer has a second melt index, and the third layer has a third melt index, wherein the second melt index is 3.5 g / 10 minutes to 10.0 g / 10 minutes, the first melt index and the third melt index are each independently less than 3.5 g / 10 minutes, and the difference between the second melt index and the first melt index and the difference between the second melt index and the third melt index are each independently 0.2 g / 10 minutes to 8.5 g / 10 minutes.

[0006] In some embodiments of the present invention, the first melt index and the third melt index are each independently 1.5 g / 10 min to 3.3 g / 10 min.

[0007] In some embodiments of the present invention, the first melt index, the second melt index, and the third melt index are measured according to ASTM D1238 at 190° C. and a load of 2.16 kg.

[0008] In some embodiments of the present invention, the first, second, and third layers each independently comprise polyvinyl acetal, and the polyvinyl acetal can be selected from the group consisting of polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl valeral, polyvinyl hexyl acetal, and combinations thereof. In a preferred embodiment of the present invention, the first, second, and third layers each independently comprise polyvinyl butyral.

[0009] In some embodiments of the present invention, the polyvinyl acetal contained in the second layer has an acetalization degree of 56 mol % to 74 mol %, an acetylation degree of 5 mol % to 15 mol %, and a hydroxyl content of 20 mol % to 30 mol %.

[0010] In some embodiments of the present invention, the polyvinyl acetal contained in the first layer and the third layer independently has an acetalization degree of 60 mol % to 75 mol %, an acetylation degree of 0.1 mol % to 5 mol %, and a hydroxyl content of 20 mol % to 35 mol %.

[0011] In some embodiments of the present invention, the polyvinyl acetal contained in the second layer has a number average molecular weight (Mn) of 100,000 to 240,000.

[0012] In some embodiments of the present invention, the number average molecular weight (Mn) of the polyvinyl acetal contained in the first layer and the third layer is independently 90,000 to 120,000.

[0013] In some embodiments of the present invention, the first layer, the second layer, and the third layer each independently further contain a plasticizer.

[0014] In some embodiments of the present invention, the first layer, the second layer, and the third layer each independently further contain a plasticizer. Based on 100 parts by weight of the polyvinyl acetal contained in the first layer, the first layer contains 30 to 50 parts by weight of the plasticizer; based on 100 parts by weight of the polyvinyl acetal contained in the second layer, the second layer contains 55 to 85 parts by weight of the plasticizer; and based on 100 parts by weight of the polyvinyl acetal contained in the third layer, the third layer contains 30 to 50 parts by weight of the plasticizer.

[0015] Another object of the present invention is to provide a laminated glass comprising a first glass sheet, an intermediate film, and a second glass sheet in sequence, wherein the intermediate film is the polymer film as described above.

[0016] In order to make the above-mentioned objectives, technical features and advantages of the present invention more obvious and easy to understand, some specific implementation plans are described in detail below. DETAILED DESCRIPTION

[0017] Some specific embodiments according to the present invention will be described in detail below; the present invention can be practiced in a variety of different forms of embodiments, and the protection scope of the present invention should not be limited to the specific embodiments.

[0018] Unless otherwise stated, the terms “a”, “an”, “the” and similar terms used in this specification and the claims should be understood to include both the singular and the plural.

[0019] Unless otherwise specified, the terms “first,” “second,” and the like used in this specification and the claims are merely used to distinguish between described elements or components and have no special meanings and are not used to represent a sequential order.

[0020] In this specification and claims, "melt index (MI)" is measured according to ASTM D 1238 at 190°C and a load of 2.16 kg.

[0021] In this specification and claims, the unit of number average molecular weight (Mn) is "Dalton".

[0022] The present invention offers advantages over existing technologies in that the provided polymer film exhibits good structural uniformity and can be used to produce laminated glass with excellent sound insulation and no optical defects. The following provides a detailed description of the present polymer film and its related applications.

[0023] 1. Polymer film

[0024] 1.1. Properties of polymer films

[0025] The polymer film of the present invention comprises a first layer, a second layer and a third layer in sequence, and both surfaces of the second layer (ie, the sound insulation intermediate layer) are in contact with the first layer and the third layer respectively.

[0026] In the polymer film of the present invention, the second layer has a second melt index, and the second melt index is 3.5 g / 10 min to 10.0 g / 10 min, for example, 3.5 g / 10 min, 3.6 g / 10 min, 3.7 g / 10 min, 3.8 g / 10 min, 3.9 g / 10 min, 4.0 g / 10 min, 4.1 g / 10 min, 4.2 g / 10 min, 4.3 g / 10 min, 4.4 g / 10 min, 4.5 g / 10 min, 4.6 g / 10 min, 4.7 g / 10 min, 4.8 g / 10 min, 4.9 g / 10 min, 5.0 g / 10 min, 5.1 g / 10 min, 5.2 g / 10 min, 5.3 g / 10 min, 5.4 g / 10 min, 5.5 g / 10 min, 5.6 g / 10 min, 5.7 g / 10 min, 5.8 g / 10 min, 5.9 g / 10 min, 5.1 g / 10 min, 5. .8g / 10 minutes, 4.9g / 10 minutes, 5.0g / 10 minutes, 5.1g / 10 minutes, 5.2g / 10 minutes, 5.3g / 10 minutes, 5.4g / 10 minutes, 5.5g / 10 minutes, 5.6g / 10 minutes, 5.7g / 10 minutes, 5.8g / 10 minutes, 5.9g / 10 minutes, 6.0g / 10 minutes, 6.1g / 10 minutes, 6.2g / 10 minutes, 6.3g / 10 minutes, 6.4g / 10 minutes, 6.5g / 10 minutes, 6.6g / 10 minutes, 6.7 g / 10 minutes, 6.8 g / 10 minutes, 6.9 g / 10 minutes, 7.0 g / 10 minutes, 7.1 g / 10 minutes, 7.2 g / 10 minutes, 7.3 g / 10 minutes, 7.4 g / 10 minutes, 7.5 g / 10 minutes, 7.6 g / 10 minutes, 7.7 g / 10 minutes, 7.8 g / 10 minutes, 7.9 g / 10 minutes, 8.0 g / 10 minutes, 8.1 g / 10 minutes, 8.2 g / 10 minutes, 8.3 g / 10 minutes, 8.4 g / 10 minutes The melt index of the second layer can be 8.5 g / 10 min, 8.6 g / 10 min, 8.7 g / 10 min, 8.8 g / 10 min, 8.9 g / 10 min, 9.0 g / 10 min, 9.1 g / 10 min, 9.2 g / 10 min, 9.3 g / 10 min, 9.4 g / 10 min, 9.5 g / 10 min, 9.6 g / 10 min, 9.7 g / 10 min, 9.8 g / 10 min, 9.9 g / 10 min, or 10.0 g / 10 min, or a range between any two of the foregoing values. The second layer having the above melt index can reduce acoustic vibrations and optimize sound insulation.

[0027] In the polymer film of the present invention, the first layer has a first melt index, and the third layer has a third melt index. The first melt index and the third melt index are each independently less than 3.5 g / 10 minutes, preferably, each independently from 1.5 g / 10 minutes to 3.3 g / 10 minutes, for example, 1.5 g / 10 minutes, 1.6 g / 10 minutes, 1.7 g / 10 minutes, 1.8 g / 10 minutes, 1.9 g / 10 minutes, 2.0 g / 10 minutes, 2. 1 g / 10 min, 2.2 g / 10 min, 2.3 g / 10 min, 2.4 g / 10 min, 2.5 g / 10 min, 2.6 g / 10 min, 2.7 g / 10 min, 2.8 g / 10 min, 2.9 g / 10 min, 3.0 g / 10 min, 3.1 g / 10 min, 3.2 g / 10 min, 3.3 g / 10 min, or 3.4 g / 10 min, or within the range consisting of any two of the above values.

[0028] In the polymer film of the present invention, the difference between the second melt index and the first melt index and the difference between the second melt index and the third melt index are each independently 0.2 g / 10 min to 8.5 g / 10 min, for example, 0.2 g / 10 min, 0.3 g / 10 min, 0.4 g / 10 min, 0.5 g / 10 min, 0.6 g / 10 min, 0.7 g / 10 min, 0.8 g / 10 min, 0.9 g / 10 min, 1.0 g / 10 min, 1.1 g / 10 min, 1.2 g / 10 min, 1.3 g / 10 min, 1.4 g / 10 min, 1.5 g / 10 min, 1.6 g / 10 min, 1.7 g / 10 min, 1 .8g / 10 minutes, 1.9g / 10 minutes, 2.0g / 10 minutes, 2.1g / 10 minutes, 2.2g / 10 minutes, 2.3g / 10 minutes, 2.4g / 10 minutes, 2.5g / 10 minutes, 2.6g / 10 minutes, 2.7g / 10 minutes, 2.8g / 10 minutes, 2.9g / 10 minutes, 3.0g / 10 minutes, 3.1g / 10 minutes, 3.2g / 10 minutes, 3.3g / 10 minutes, 3.4g / 10 minutes, 3.5g / 10 minutes, 3.6g / 10 minutes, 3.7g / 10 minutes, 3.8g / 10 minutes, 3.9g / 10 minutes, 4.0g / 10 minutes, 4.1g / 10 minutes, 4.2g / 10 minutes, 4.3g / 10 minutes, 4.4g / 10 minutes, 4.5g / 10 minutes, 4.6g / 10 minutes, 4.7g / 10 minutes, 4.8g / 10 minutes, 4.9g / 10 minutes, 5.0g / 10 minutes, 5.1g / 10 minutes, 5.2g / 10 minutes, 5.3g / 10 minutes, 5.4g / 10 minutes, 5.5g / 10 minutes, 5.6g / 10 minutes, 5.7g / 10 minutes, 5.8g / 10 minutes, 5.9g / 10 minutes, 6.0g / 10 minutes, 6.1g / 10 minutes, 6.2g / 10 minutes, 6.3g / 10 minutes, 6.4g / 1 g / 10 minutes, 8.0 g / 10 minutes, 8.1 g / 10 minutes, 8.2 g / 10 minutes, 8.3 g / 10 minutes, 8.4 g / 10 minutes, or 8.5 g / 10 minutes, or within the range consisting of any two of the above values.

[0029] Research has found that only when the melt index of the first, second, and third layers each falls within the specified range, and the difference in melt index between the first and second layers, as well as the difference in melt index between the third and second layers, also falls within the specified range, can a polymer film with good structural uniformity be provided, thereby achieving laminated glass with excellent sound insulation and no optical defects. Good structural uniformity means that the first, second, and third layers of the polymer film are intact and continuous throughout the film, without discontinuities in the second layer, and that the second layer has the desired thickness and good thickness uniformity (with a thickness deviation of no more than 0.025 mm).

[0030] 1.2. Composition of polymer films

[0031] The polymer film of the present invention may include, in sequence, a first layer, a second layer, and a third layer, with both surfaces of the second layer in contact with the first layer and the third layer, respectively. That is, the second layer is located between the first and third layers. Alternatively, the polymer film of the present invention may essentially consist of, in sequence, the first layer, the second layer, and the third layer, with both surfaces of the second layer in contact with the first layer and the third layer, respectively. Still further, the polymer film of the present invention may consist of, in sequence, the first layer, the second layer, and the third layer, with both surfaces of the second layer in contact with the first layer and the third layer, respectively.

[0032] In the polymer film of the present invention, the first, second, and third layers each independently comprise polyvinyl acetal as an essential component, and the first, second, and third layers may each independently further comprise other optional components, such as a plasticizer or other conventional additives, as needed. Herein, "the first, second, and third layers each independently comprise polyvinyl acetal" means that the first, second, and third layers each comprise polyvinyl acetal, and the polyvinyl acetals contained in each layer may be the same or different. In some embodiments of the present invention, the first, second, and third layers each independently comprise polyvinyl acetal and a plasticizer, wherein the polyvinyl acetal and plasticizer contained in each layer may be the same or different. Alternatively, the first, second, and third layers each independently consist essentially of polyvinyl acetal and a plasticizer, wherein the polyvinyl acetal and plasticizer contained in each layer may be the same or different. Alternatively, the first, second, and third layers each independently consist essentially of polyvinyl acetal and a plasticizer, wherein the polyvinyl acetal and plasticizer contained in each layer may be the same or different. Furthermore, the first, second, and third layers each independently consist of polyvinyl acetal and a plasticizer, wherein the polyvinyl acetal and plasticizer contained in each layer may be the same or different.

[0033] The first, second, and third layers of the polymer film of the present invention may each independently be a monolayer film consisting of a single layer, or a multilayer film consisting of multiple layers, as long as the polymer film as a whole meets the aforementioned melt index conditions. In some embodiments of the present invention, the first, second, and third layers are each a monolayer film consisting of a single layer.

[0034] 1.2.1. Polyvinyl acetal

[0035] Examples of polyvinyl acetals include, but are not limited to, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, polyvinyl valeral, and polyvinyl hexyl acetal. Each of the aforementioned polyvinyl acetals may be used alone or in combination. In a preferred embodiment of the present invention, the polyvinyl acetal is poly(vinyl butyral).

[0036] 1.2.1.1. Polyvinyl acetal contained in the second layer

[0037] In some embodiments of the present invention, the number average molecular weight (Mn) of the polyvinyl acetal contained in the second layer is 100,000 to 240,000, for example, 100,000, 105,000, 110,000, 115,000, 120,000, 125,000, 130,000, 135,000, 140,000, 145,000, 150,000, 155,000. , 160,000, 165,000, 170,000, 175,000, 180,000, 185,000, 190,000, 195,000, 200,000, 205,000, 210,000, 215,000, 220,000, 225,000, 230,000, 235,000, or 240,000, or within a range consisting of any two of the above values. Generally speaking, a higher number average molecular weight of a polymer indicates a higher degree of polymerization, and correspondingly, the poorer the fluidity of the polymer and the lower the melt index. Conversely, a lower number average molecular weight of a polymer indicates a higher melt index.

[0038] In some embodiments of the present invention, the acetal group content (i.e., degree of acetalization) of the polyvinyl acetal contained in the second layer may be 56 mol% to 74 mol%, for example, 56 mol%, 56.5 mol%, 57 mol%, 57.5 mol%, 58 mol%, 58.5 mol%, 59 mol%, 59.5 mol%, 60 mol%, 60.5 mol%, 61 mol%, 61.5 mol%, 62 mol%, 62.5 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 76 mol%, 77 mol%, 78 mol%, 79 mol%, 80 mol%, 81 mol%, 82 mol%, 83 mol%, 84 mol%, 85 mol%, 86 mol%, 87 mol%, 88 mol%, 89 mol%, 90 mol%, 91 mol%, 92 mol%, 93 mol%, 94 mol%, 95 mol%, 96 mol%, 97 mol%, 98 mol%, 99 mol%, 100 mol%, 101 mol%, 102 mol%, 103 mol%, 104 mol%, 105 mol%, 106 mol%, 107 mol%, 108 mol%, 109 mol%, 110 %, 63 mol%, 63.5 mol%, 64 mol%, 64.5 mol%, 65 mol%, 65.5 mol%, 66 mol%, 66.5 mol%, 67 mol%, 67.5 mol%, 68 mol%, 68.5 mol%, 69 mol%, 69.5 mol%, 70 mol%, 70.5 mol%, 71 mol%, 71.5 mol%, 72 mol%, 72.5 mol%, 73 mol%, 73.5 mol%, or 74 mol%, or a range consisting of any two of the foregoing values. In a preferred embodiment of the present invention, the degree of acetalization of the polyvinyl acetal contained in the second layer is 60 mol% to 71 mol%, based on the total molar number of acetal groups, acetyl groups, and hydroxyl groups in the polyvinyl acetal contained in the second layer.

[0039] In some embodiments of the present invention, the acetyl content (i.e., degree of acetylation) of the polyvinyl acetal contained in the second layer may be 5 mol% to 15 mol%, based on the total moles of acetal groups, acetyl groups, and hydroxyl groups in the polyvinyl acetal contained in the second layer, for example, 5 mol%, 5.5 mol%, 6 mol%, 6.5 mol%, 7 mol%, 7.5 mol%, 8 mol%, 8.5 mol%, 9 mol%, 9.5 mol%, 10 mol%, 10.5 mol%, 11 mol%, 11.5 mol%, 12 mol%, 12.5 mol%, 13 mol%, 13.5 mol%, 14 mol%, 14.5 mol%, or 15 mol%, or a range between any two of the foregoing values. In a preferred embodiment of the present invention, the degree of acetylation of the polyvinyl acetal contained in the second layer is 7 mol% to 12 mol%, based on the total moles of acetal groups, acetyl groups, and hydroxyl groups in the polyvinyl acetal contained in the second layer.

[0040] In some embodiments of the present invention, the hydroxyl content of the polyvinyl acetal contained in the second layer may be 20 mol% to 30 mol%, based on the total moles of acetal groups, acetyl groups, and hydroxyl groups in the polyvinyl acetal contained in the second layer, for example, 20 mol%, 20.5 mol%, 21 mol%, 21.5 mol%, 22 mol%, 22.5 mol%, 23 mol%, 23.5 mol%, 24 mol%, 24.5 mol%, 25 mol%, 25.5 mol%, 26 mol%, 26.5 mol%, 27 mol%, 27.5 mol%, 28 mol%, 28.5 mol%, 29 mol%, 29.5 mol%, or 30 mol%, or a range between any two of the foregoing values. In a preferred embodiment of the present invention, the hydroxyl content of the polyvinyl acetal contained in the second layer is 22 mol% to 28 mol%, based on the total moles of acetal groups, acetyl groups, and hydroxyl groups in the polyvinyl acetal contained in the second layer. The lower the hydroxyl content, the more plasticizer the polyvinyl acetal can absorb.

[0041] 1.2.1.2. Polyvinyl acetal contained in the first and third layers

[0042] In some embodiments of the present invention, the number average molecular weight (Mn) of the polyvinyl acetal contained in the first layer and the third layer is independently 90,000 to 120,000, for example, 90,000, 91,000, 92,000, 93,000, 94,000, 95,000, 96,000, 97,000, 98,000, 99,000, 100,000, 101,000, 102,000, 103,000, 104,000, 105,000, 106,000, 107,000, 108,000, 109,000, 110,000, 111,000, 112,000, 113,000, 114,000, 115,000, 116,000, 117,000, 118,000, 119,000, 120,000, 0000, 03000, 104000, 105000, 106000, 107000, 108000, 109000, 110000, 111000, 112000, 113000, 114000, 115000, 116000, 117000, 118000, 119000, or 120000, or within the range formed by any two of the above values.

[0043] In some embodiments of the present invention, the acetal group content (i.e., degree of acetalization) of the polyvinyl acetal contained in each of the first layer and the third layer may be independently 60 mol% to 75 mol%, for example, 60 mol%, 60.5 mol%, 61 mol%, 61.5 mol%, 62 mol%, 62.5 mol%, 63 mol%, 63.5 mol%, 64 mol%, 64.5 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 76 mol%, 77 mol%, 78 mol%, 79 mol%, 80 mol%, 81 mol%, 82 mol%, 83 mol%, 84 mol%, 85 mol%, 86 mol%, 87 mol%, 88 mol%, 89 mol%, 90 mol%, 91 mol%, 92 mol%, 93 mol%, 94 mol%, 95 mol%, 96 mol%, 97 mol%, 98 mol%, 99 mol%, 100 mol%, 101 mol%, 102 mol%, 103 mol%, 104 mol%, 105 mol%, 106 mol%, 107 mol%, 108 mol%, 109 mol%, 110 mol%, 111 mol%, 112 mol%, 113 mol%, 114 mol%, 115 %, 65 mol%, 65.5 mol%, 66 mol%, 66.5 mol%, 67 mol%, 67.5 mol%, 68 mol%, 68.5 mol%, 69 mol%, 69.5 mol%, 70 mol%, 70.5 mol%, 71 mol%, 71.5 mol%, 72 mol%, 72.5 mol%, 73 mol%, 73.5 mol%, 74 mol%, 74.5 mol%, or 75 mol%, or a range consisting of any two of the foregoing values. In a preferred embodiment of the present invention, the degree of acetalization of the polyvinyl acetal contained in each of the first layer and the third layer is 70 mol% to 72 mol%, based on the total moles of acetal groups, acetyl groups, and hydroxyl groups of the polyvinyl acetal contained in each of the first layer and the third layer.

[0044] In some embodiments of the present invention, the acetyl content (i.e., degree of acetylation) of the polyvinyl acetal contained in each of the first and third layers may be independently 0.1 mol% to 5 mol%, for example, 0.1 mol%, 0.5 mol%, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 3.5 mol%, 4 mol%, 4.5 mol%, or 5 mol%, based on the total moles of acetal groups, acetyl groups, and hydroxyl groups in the polyvinyl acetal contained in each of the first and third layers, or a range between any two of the foregoing values. In a preferred embodiment of the present invention, the degree of acetylation of the polyvinyl acetal contained in each of the first and third layers is 0.5 mol% to 1.5 mol%, based on the total moles of acetal groups, acetyl groups, and hydroxyl groups in the polyvinyl acetal contained in each of the first and third layers.

[0045] In some embodiments of the present invention, based on the total molar number of acetal groups, acetyl groups, and hydroxyl groups of the polyvinyl acetal contained in each of the first layer and the third layer, the hydroxyl group content of the polyvinyl acetal contained in each of the first layer and the third layer may be 20 mol% to 35 mol%, for example, 20 mol%, 20.5 mol%, 21 mol%, 21.5 mol%, 22 mol%, 22.5 mol%, 23 mol%, 23.5 mol%, 24 mol%, 24.5 mol%, 25 %, 25.5 mol%, 26 mol%, 26.5 mol%, 27 mol%, 27.5 mol%, 28 mol%, 28.5 mol%, 29 mol%, 29.5 mol%, 30 mol%, 30.5 mol%, 31 mol%, 31.5 mol%, 32 mol%, 32.5 mol%, 33 mol%, 33.5 mol%, 34 mol%, 34.5 mol%, or 35 mol%, or a range consisting of any two of the foregoing values. In a preferred embodiment of the present invention, the hydroxyl content of the polyvinyl acetal contained in each of the first layer and the third layer is 27 mol% to 29 mol%, based on the total molar number of acetal groups, acetyl groups, and hydroxyl groups of the polyvinyl acetal contained in each of the first layer and the third layer.

[0046] 1.2.2. Plasticizers

[0047] Herein, plasticizer refers to a chemical substance that can change the plasticity of thermoplastic resin, and may also be referred to as plasticizer. Generally speaking, the higher the amount of plasticizer added, the higher the melt index of the polymer film. There is no particular limitation on the type of plasticizer, and the plasticizers contained in the first layer, the second layer, and the third layer may be the same or different. Examples of plasticizers include, but are not limited to, esters of polyacids or polyols, such as triethylene glycol bis(2-ethylhexanoate), tetraethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), tetraethylene glycol bis(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl adipate, cyclohexyl hexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, bis[2-(2-butoxyethoxy)ethyl adipate], polymeric adipate (polymeric adipate), dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, propylene glycol dibenzoate, diisononyl phthalate, dibutoxyethyl terephthalate, castor oil, methyl ricinoleate, soybean oil, epoxidized soybean oil, and combinations thereof. In the accompanying examples, triethylene glycol bis(2-ethylhexanoate) was used as a plasticizer.

[0048] In some embodiments of the present invention, the amount of plasticizer in the first layer is 30 to 50 parts by weight, based on 100 parts by weight of the polyvinyl acetal in the first layer, for example, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 parts by weight, or a range between any two of the foregoing values. In a preferred embodiment of the present invention, the amount of plasticizer in the first layer is 38 to 44 parts by weight, based on 100 parts by weight of the polyvinyl acetal in the first layer.

[0049] In some embodiments of the present invention, based on 100 parts by weight of the polyvinyl acetal contained in the second layer, the amount of plasticizer contained in the second layer is 55 to 85 parts by weight, for example, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 81 parts by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, or 85 parts by weight, or within a range consisting of any two of the above values. In a preferred embodiment of the present invention, the content of the plasticizer in the second layer is 60 to 80 parts by weight based on 100 parts by weight of the polyvinyl acetal in the second layer.

[0050] In some embodiments of the present invention, the amount of plasticizer in the third layer is 30 to 50 parts by weight, based on 100 parts by weight of the polyvinyl acetal in the third layer, for example, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 parts by weight, or a range between any two of the foregoing values. In a preferred embodiment of the present invention, the amount of plasticizer in the third layer is 38 to 44 parts by weight, based on 100 parts by weight of the polyvinyl acetal in the third layer.

[0051] 1.2.3. Other existing additives

[0052] Existing additives may include any substance that can adaptably improve the processability of the polymer film during the manufacturing process or impart specific functionality to the polymer film. Such specific functionality includes, but is not limited to, one or more of the following: heat insulation, reflection, anti-reflection, refraction, anti-refraction, light splitting, and light reduction.

[0053] Examples of existing additives include, but are not limited to, dyes, pigments, stabilizers, antioxidants, flame retardants, infrared absorbers, infrared blockers, ultraviolet absorbers, ultraviolet stabilizers, lubricants, dispersants, surfactants, chelating agents, coupling agents, binders, and adhesion control agents. For example, a polymer film may contain a dye or pigment to form a colored polymer film, or contain an ultraviolet absorber or an infrared absorber to form a polymer film with UV protection or infrared protection. Each of the aforementioned additives may be used alone or in combination, and may be added to one or more of the first, second, and third layers of the polymer film as needed.

[0054] 1.3. Other properties of polymer films

[0055] Under the premise of meeting the specified melt index conditions, the total thickness, the thickness of the first layer, the thickness of the second layer and the thickness of the third layer of the polymer film of the present invention can be adjusted according to actual needs. Generally speaking, the total thickness of the polymer film can be 0.1 mm to 2.5 mm, for example, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm The thickness of the polymer film is preferably 1.5 mm, 1.6 mm, 1.7 mm, 1.75 mm, 1.8 mm, 1.85 mm, 1.9 mm, 1.95 mm, 2.0 mm, 2.05 mm, 2.1 mm, 2.15 mm, 2.2 mm, 2.25 mm, 2.3 mm, 2.35 mm, 2.4 mm, 2.45 mm, or 2.5 mm, or within a range consisting of any two of the foregoing values. In the following embodiments, the total thickness of the polymer film is between 0.76 mm and 0.85 mm.

[0056] In some embodiments of the present invention, the thickness of the first layer and the third layer may each independently be 250 μm to 450 μm, for example, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, 300 μm, 310 μm, 320 μm, 330 μm, 340 μm, 350 μm, 360 μm, 370 μm, 380 μm, 390 μm, 400 μm, 410 μm, 420 μm, 430 μm, 440 μm, or 450 μm, or within a range consisting of any two of the above values.

[0057] In some embodiments of the present invention, the thickness of the second layer may be 50 μm to 250 μm, for example, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, or 250 μm, or within a range consisting of any two of the above values.

[0058] 1.4. Preparation of polymer membranes

[0059] The method for preparing the polymer film of the present invention is not particularly limited. For example, polyvinyl acetal can be mixed with selected ingredients (such as a plasticizer), dry-mixed, and kneaded to form a polymer film composition. The polymer film composition can then be formed into a film using existing film preparation methods, and the surface of the polymer film can be mechanically embossed. Examples of such film preparation methods include, but are not limited to, calendaring, casting, extrusion tentering, direct extrusion, and extrusion blow molding.

[0060] In some embodiments of the present invention, a polymer film is prepared as follows, but the present invention is not limited thereto: a first polymer film composition is provided for preparing the first layer and the third layer, and a second polymer film composition is provided for preparing the second layer; the first polymer film composition and the second polymer film composition are placed in a co-extruder to form the polymer film of the present invention by co-extrusion.

[0061] The first polymer film composition and the second polymer film composition can be independently prepared by the following method, but the present invention is not limited thereto: preheating the selected resin-state polyvinyl acetal in an oven; dry-mixing the preheated polyvinyl acetal with a plasticizer; and then mixing the dry-mixed mixture using a twin-screw mixer to obtain the desired first polymer film composition or second polymer film composition.

[0062] Without being limited by theory, the melt index of a polymer film can be adjusted by controlling the functional group content of the polymer, the plasticizer content of the polymer film, and the uniformity of plasticizer absorption into the polymer. The uniformity of plasticizer absorption into the polymer can be adjusted by controlling the preheating temperature, dry mixing temperature, dry mixing time, mixing temperature, and mixing time during the polymer film preparation process. Generally speaking, preheating can open the pores between the resins and allow the resin to develop some fluidity, facilitating subsequent mixing with the plasticizer. A higher dry mixing temperature helps open the pores between the resins, facilitating plasticizer absorption, while a longer dry mixing time ensures a more uniform mixing of the resin and plasticizer. A higher mixing temperature can improve the fluidity of the plasticizer, thereby enhancing the compatibility between the plasticizer and the resin, while a longer mixing time ensures a more uniform mixing of the resin and plasticizer. Furthermore, the functional group content can also affect the uniformity of plasticizer absorption into the polymer. Based on the above, in the following examples of the present invention, in addition to adjusting the composition ratio of the first polymer film composition and the second polymer film composition, the following conditions are also controlled to prepare a polymer film having the melt index characteristics of the present invention: preheating temperature of 30°C to 45°C; dry mixing temperature of 30°C to 45°C; dry mixing time of 2 minutes to 3 minutes; kneading temperature of 180°C to 210°C; and kneading time of 8 minutes to 12 minutes.

[0063] The polymer film of the present invention formed by co-extrusion can be further formed with a concave-convex structure on the surface of the polymer film by preheating and mechanical embossing to facilitate exhaust. Mechanical embossing refers to the use of a roller to create textures on the surface of the formed polymer film. The methods of mechanical embossing include, but are not limited to, an embossing wheel method and a calendering wheel method, among which the embossing wheel method is preferred. There is no special restriction on the pattern of mechanical embossing, for example, it includes diamond, linear, zigzag, square, conical, circular, approximately circular, and irregular shapes. The aforementioned pattern of textures can be used alone or in combination. The preheating and mechanical embossing conditions can be adaptively adjusted according to the composition of the polymer film used.

[0064] 2. Laminated glass

[0065] The polymer film of the present invention can be used to prepare laminated glass. Therefore, the present invention also provides a laminated glass, which comprises a first glass sheet, an intermediate film and a second glass sheet in sequence, wherein the intermediate film is the polymer film as described above.

[0066] The first and second glass sheets can be the same or different and can be any conventional glass sheet used to make laminated glass, such as float glass, tempered glass, wired glass, or ordinary flat glass, but the present invention is not limited thereto. In the following examples, float glass is used as the first and second glass sheets.

[0067] The laminated glass of the present invention can be produced by the existing laminated glass production method in the relevant technical field. Generally speaking, the production method of laminated glass can be roughly divided into a pre-pressing step and a positive pressing step. The pre-pressing step is as follows. First, a polymer film is sandwiched between two glass sheets to obtain a laminate. Then, the conveying speed of the conveyor belt of the roller press is set to 2m / min (meters / minute) to 8m / min, the temperature of the oven is set to 160°C to 190°C, and the pressure of the roller is set to 3kg / cm 2 (kg / cm2) to 10kg / cm 2 , place the laminate on a conveyor belt and pass it through an oven and rollers in sequence, with the distance between the rollers set to 4.5 mm to 6.5 mm. Afterwards, the rolled laminate is cooled to room temperature to complete the pre-pressing. The pre-pressed laminate is then placed in an autoclave for a positive pressing step. The positive pressing step includes hot pressing the pre-pressed laminate under high temperature and high pressure conditions for 100 minutes to 150 minutes to produce laminated glass. Generally speaking, the high temperature and high pressure conditions can be a pressure of 10 bar to 15 bar and a temperature of 100°C to 150°C.

[0068] 3. Examples

[0069] 3.1. Measurement method description

[0070] The present invention is further illustrated by the following specific examples, wherein the measuring instruments and methods used are as follows:

[0071] Determination of acetal degree, acetylation degree and hydroxyl content of polyvinyl acetal

[0072] The acetalization degree, acetylation degree and hydroxyl content of polyvinyl acetal are measured according to JIS K6728:1977.

[0073] 《Measurement of Molecular Weight of Polyvinyl Acetal》

[0074] The molecular weight distribution of polyvinyl acetal was measured by gel permeation chromatography (GPC). Polyvinyl acetal was dissolved in tetrahydrofuran (THF). GPC analysis was performed under the following conditions. The molecular weight (Mn) was calculated as the ratio of the area to the corresponding polystyrene standard (Waters PS STD).

[0075] Device: Waters 1515PUMP system;

[0076] Detector: Waters 2414RI;

[0077] Elution conditions: 1.0 mL / min, THF;

[0078] Column: Waters Styragel HR5 THF, Waters Styragel HR4 THF, Waters;

[0079] Styragel HR3 THF, Waters Styragel HR1 THF;

[0080] 《Measuring Melt Index》

[0081] According to ASTM D1238, the melt index of the polymer film is measured using a melt index tester (model: D4002HV, purchased from Dynisco), and the weight of the effluent is calculated according to the manual operation method (Method A). The test conditions are 190°C and 2.16 kg load, and the sample weight is 6 grams. The detailed measurement steps are as follows. First, the sample is placed in a constant temperature and humidity chamber at 23°C and 25% relative humidity for 2 hours. Then, the melt index tester is turned on and heated to 190°C, and then the sample is placed in the barrel and pressed tightly. After placing the piston rod and weight (the total weight of the two is 2.16 kg), the time is set for 120 seconds, and the effluent during this period is not counted. The formal test begins after 120 seconds, and the effluent is taken every 200 seconds for weight measurement, for a total of 3 times, and the melt index is calculated according to the following formula. The unit of the melt index is grams / 10 minutes.

[0082]

[0083] Evaluation of Continuous Layer Structures

[0084] An optical microscope (model: BX51, purchased from Olympus) was used to observe whether the structure of each layer of the polymer film was continuous. The polymer film was cut into samples of 100 cm x 5 cm, where 100 cm was the length in the perpendicular machine direction and 5 cm was the length in the machine direction. A clamping fixture was used to clamp the two short sides of the sample so that the long side of the film (i.e., the cut surface) was facing the objective lens. The optical microscope was configured as follows: the objective lens magnification was set to 5x. The evaluation criteria were as follows: when the structure of each layer in the polymer film was continuous and uninterrupted, it indicated good structural uniformity and was recorded as "○"; when the structure of any layer in the polymer film was interrupted, it indicated poor structural uniformity and was recorded as "×".

[0085] Layer Thickness Evaluation

[0086] The thickness of the second layer (middle layer) was measured using an optical microscope (model: BX51, purchased from Olympus), and the thickness was calculated using the built-in software of the optical microscope (Motic Image Plus 2.0). The polymer film was cut into samples of 100 cm × 5 cm, where 100 cm is the length in the vertical machine direction and 5 cm is the length in the machine direction. The two short sides of the sample were clamped using a clamping fixture so that the long side of the film (i.e., the cut surface) was facing the objective lens. The configuration of the optical microscope was as follows: the objective lens magnification was set to 5 times. The measurement method was as follows: starting from the left border, the thickness of the second layer was measured at 1 cm, 25 cm, 50 cm, 75 cm and 100 cm, for a total of five values. The evaluation criteria are as follows: if all five values ​​are between 0.1 mm and 0.15 mm, record as "○"; if any value falls outside the range of 0.1 mm to 0.15 mm, record as "×"; if a total of five values ​​cannot be measured, for example, if only four values ​​are measured, record as "NA (unable to analyze)".

[0087] Additionally, subtract the minimum from the maximum of the five values ​​to calculate the second layer's thickness deviation and record this value. A deviation of 0.025 mm or less indicates good thickness uniformity, while a deviation greater than 0.025 mm indicates poor thickness uniformity. If all five thickness values ​​cannot be measured, record the second layer's thickness deviation as "NA (Unable to Analyze)."

[0088] Loss Coefficient Evaluation

[0089] The loss coefficient of laminated glass was evaluated using the mechanical impedance measurement (MIM) method according to ISO 16940:2008. Sample preparation was as follows: a polymer film 300 mm long and 25 mm wide was sandwiched between two sheets of clear float glass (300 mm long, 25 mm wide, and 2 mm thick) to form a laminate. The laminate was then subjected to a pre-lamination and positive lamination step to produce the laminated glass, where the pre-lamination and positive lamination steps were as described above. The laminated glass was then placed in a constant temperature and humidity chamber at 23°C and 55% relative humidity for 2 hours. The loss coefficient was then measured as follows: First, the center of the laminated glass was fixed to a vibration shaker and shaken at an ambient temperature of 20°C. Next, an impedance head was used to measure the force and frequency of the oscillations of the laminated glass. An analysis system then converted these values ​​into a damping loss factor, calculated using the half-power method for the first vibration mode. A damping loss factor greater than 0.25 at 20°C indicates that the laminated glass provides good sound insulation.

[0090] Evaluation of Optical Distortion

[0091] First, prepare a 30 cm x 30 cm laminated glass sample as a test sample. Also, prepare a projector (model: NP-P451X, purchased from NEC, with a light source of 4500 ANSI lumens), a sample holder, and a white screen. Place the projector, sample holder, and white screen in a darkroom, with the sample holder positioned between the projector and the white screen. The distance between the projector, sample holder, and white screen is 1.5 meters. Place the test sample on the sample holder and adjust the angle so that the sample is tilted 15 degrees toward the projector relative to the vertical ground. Turn on the projector light source, passing light through the test sample and onto the white screen. Observe the white screen for any noticeable difference in brightness. If no wispy streaks (light ripples) are present in the laminated glass, record this as "No." If wispy streaks (light ripples) are present, record this as "Present."

[0092] 3.2. Preparation and property measurement of polymer films

[0093] 3.2.1. First and third layers of polymer film

[0094] 100 parts by weight of polyvinyl butyral (PVB, purchased from Changchun Petrochemical Co., Ltd.) was preheated in an oven at 30°C to 45°C for 1 minute; then, the preheated PVB was dry-mixed with a plasticizer at a first dry-mixing temperature for a first dry-mixing time to obtain a first dry-mixed mixture; thereafter, the first dry-mixed mixture was kneaded using a twin-screw mixer at the first kneading temperature for a first kneading time to obtain the first polymer film compositions of Examples 1 to 11 and Comparative Examples 1 to 9, respectively. The amount of plasticizer used is shown in Tables 1-1 and 2-1, and the first dry-mixing temperature, first dry-mixing time, first kneading temperature, and first kneading time are shown in Tables 1-2 and 2-2. The Mn, acetalization degree, acetylation degree, and hydroxyl content ratio of the PVB used were measured according to the methods described above, and the results are recorded in Tables 1-1 and 2-1. The units of acetalization degree, acetylation degree, and hydroxyl content ratio are all mole %.

[0095] The first polymer film compositions of Examples 1-11 and Comparative Examples 1-9 were extruded into single-layer polymer films (hereinafter referred to as "first single-layer polymer films") in an extruder. The melt index of each first single-layer polymer film was measured according to the method described above, and the results are reported in Tables 1-5 and 2-5. Each of the first polymer film compositions serves as the material for the first and third layers of the polymer films of Examples 1-11 and Comparative Examples 1-9, respectively. Therefore, the melt index of each first single-layer polymer film represents the melt index of the first and third layers of the polymer film, namely, the first and third melt indexes. Because the third melt index is the same as the first melt index, only the results related to the first melt index are reported in the table.

[0096] 3.2.2. Second layer of polymer film

[0097] 100 parts by weight of PVB were preheated in an oven at 30°C to 45°C for 1 minute; then, the preheated PVB was dry-mixed with a plasticizer at a second dry-mixing temperature for a second dry-mixing time to obtain a second dry-mixed mixture; thereafter, the second dry-mixed mixture was kneaded using a twin-screw mixer at the second kneading temperature for a second kneading time to obtain the second polymer film compositions of Examples 1 to 11 and Comparative Examples 1 to 9, respectively. The amount of plasticizer used is shown in Tables 1-3 and 2-3, and the second dry-mixing temperature, second dry-mixing time, second kneading temperature, and second kneading time are shown in Tables 1-4 and 2-4. The Mn, acetalization degree, acetylation degree, and hydroxyl content ratio of the PVB used were measured according to the methods described above, and the results are recorded in Tables 1-3 and 2-3. The units of acetalization degree, acetylation degree, and hydroxyl content ratio are all molar%.

[0098] The second polymer film compositions of Examples 1-11 and Comparative Examples 1-9 were each extruded into a single-layer polymer film (hereinafter referred to as the "second single-layer polymer film"). The melt index of each second single-layer polymer film was measured according to the method described above, and the results are recorded in Tables 1-5 and 2-5. Each of the second polymer film compositions is hereinafter used as the material for the second layer of the polymer films of Examples 1-11 and Comparative Examples 1-9. Therefore, the melt index of each second single-layer polymer film represents the melt index of the second layer of the polymer film, i.e., the second melt index.

[0099] Preparation of polymer membranes

[0100] The first polymer film compositions and the second polymer film compositions of Examples 1-11 and Comparative Examples 1-9 were placed in a coextruder to form polymer films having a three-layer structure by coextrusion. The polymer films had a total thickness of 0.8 mm. The first and third layers were formed from the first polymer film composition, each having a thickness of 0.335 mm. The second layer was formed from the second polymer film composition, and had a thickness of 0.13 mm.

[0101] Afterwards, both surfaces of each polymer film were preheated and mechanically embossed to form surface textures, thereby obtaining polymer films of Examples 1 to 11 and Comparative Examples 1 to 9.

[0102] Table 1-1: Properties of the first polymer film compositions of Examples 1 to 11

[0103]

[0104] Table 1-2: Preparation parameters of the first polymer film composition of Examples 1 to 11

[0105]

[0106]

[0107] Table 1-3: Properties of the Second Polymer Film Compositions of Examples 1 to 11

[0108]

[0109] Table 1-4: Preparation parameters of the second polymer film composition of Examples 1 to 11

[0110]

[0111]

[0112] Table 1-5: Melt Index of Polymer Films of Examples 1 to 11

[0113]

[0114] Table 2-1: Properties of the first polymer film compositions of Comparative Examples 1 to 9

[0115]

[0116] Table 2-2: Preparation parameters of the first polymer film composition of Comparative Examples 1 to 9

[0117]

[0118] Table 2-3: Properties of the Second Polymer Film Compositions of Comparative Examples 1 to 9

[0119]

[0120] Table 2-4: Preparation parameters of the second polymer film compositions of Comparative Examples 1 to 9

[0121]

[0122]

[0123] Table 2-5: Melt Index of Polymer Films of Comparative Examples 1 to 9

[0124]

[0125] 3.3. Preparation and property evaluation of laminated glass

[0126] The polymer films of Examples 1 to 11 and Comparative Examples 1 to 9 were used to prepare laminated glass. First, the polymer film was cut into a size of 300 mm x 300 mm. Next, two clean transparent float glass sheets (length 300 mm, width 300 mm, thickness 2 mm) were prepared, and the cut polymer film was sandwiched between the two transparent float glass sheets to obtain a laminate. The laminate was vacuumed using a pressure wheel method for pre-pressing. The operation of the pressure wheel method is as follows: the conveying rate of the conveyor belt of the roller press is set to 4.5 m / min, the temperature of the oven is set to 180°C, and the pressure of the roller is set to 3 kg / cm 2 The laminate was placed on a conveyor belt and passed through an oven and between rollers, with the rollers set at a distance of 5 mm. The pre-laminated laminate was then placed in an autoclave at a pressure of 13 bar and a temperature of 135°C for 120 minutes, followed by cooling to room temperature to produce laminated glass.

[0127] The polymer films of Examples 1 to 11 and Comparative Examples 1 to 9 and the laminated glasses were evaluated for continuous layer structure, layer thickness, loss coefficient, and optical distortion according to the aforementioned methods. The results are recorded in Tables 3-1 and 3-2.

[0128] Table 3-1: Properties of polymer films and laminated glasses of Examples 1 to 11

[0129]

[0130]

[0131] Table 3-2: Properties of polymer films and laminated glasses of Comparative Examples 1 to 9

[0132]

[0133] As shown in Table 3-1, the polymer films of Examples 1 to 11 of the present invention exhibit continuous layer structures with good structural uniformity and a suitable and uniform second layer thickness. In particular, the laminated glass produced from these polymer films exhibited a loss coefficient exceeding 0.25, demonstrating excellent sound insulation. Furthermore, these laminated glasses exhibited no optical distortion defects.

[0134] In contrast, as shown in Table 3-2, polymer films not according to the present invention lack a continuous layer structure and a suitable and uniform second layer thickness. The resulting laminated glass exhibits a loss coefficient below 0.25, indicating poor sound insulation. Furthermore, the resulting laminated glass exhibits optical distortion. In particular, Comparative Example 1 demonstrates that if the first melt index is greater than the second melt index and the difference between the second and first melt indexes is outside the specified range, the polymer film fails to have a continuous and appropriately thick second layer. Consequently, the resulting laminated glass exhibits a loss coefficient below 0.25 and exhibits optical distortion. Comparative Examples 2, 3, and 6 demonstrate that if the difference between the second and first melt indexes falls below the specified range of the present invention, the resulting laminated glass exhibits a loss coefficient below 0.25, resulting in poor sound insulation. Comparative Examples 4, 5, and 8 demonstrate that if the difference between the second and first melt indexes exceeds the specified range of the present invention, the thickness of the polymer film's second layer is insufficient and uneven, resulting in a loss coefficient below 0.25 and optical distortion. Comparative Example 7 shows that if the second melt index is above the specified range, even if the difference between the second melt index and the first melt index falls within the specified range, the thickness of the second layer of the polymer film is still insufficient and uneven, resulting in a loss coefficient of less than 0.25 and optical distortion in the resulting laminated glass. Comparative Example 9 shows that if the second melt index is below the specified range, even if the difference between the second melt index and the first melt index falls within the specified range, the loss coefficient of the resulting laminated glass is less than 0.25, resulting in poor sound insulation.

[0135] The above embodiments are intended only to illustrate the principles and efficacy of the present invention and to illustrate the technical features of the present invention, and are not intended to limit the scope of protection of the present invention. Any modifications or arrangements that can be readily accomplished by a person skilled in the art without violating the technical principles of the present invention are within the scope of the present invention.

Claims

1. A polymer film, characterized in that It includes a first layer, a second layer, and a third layer in sequence, and two surfaces of the second layer are in contact with the first layer and the third layer respectively, the first layer has a first melt index, the second layer has a second melt index, and the third layer has a third melt index, wherein the second melt index is 3.5 g / 10 minutes to 10.0 g / 10 minutes, the first melt index and the third melt index are each independently less than 3.5 g / 10 minutes, and the difference between the second melt index and the first melt index and the difference between the second melt index and the third melt index are each independently 0.2 g / 10 minutes to 8.5 g / 10 minutes. The first layer, the second layer and the third layer each independently comprise polyvinyl acetal and a plasticizer. wherein, based on 100 parts by weight of the polyvinyl acetal contained in the first layer, the content of the plasticizer contained in the first layer is 30 parts by weight to 50 parts by weight; based on 100 parts by weight of the polyvinyl acetal contained in the second layer, the content of the plasticizer contained in the second layer is 55 parts by weight to 85 parts by weight; and based on 100 parts by weight of the polyvinyl acetal contained in the third layer, the content of the plasticizer contained in the third layer is 30 parts by weight to 50 parts by weight. The thickness of the first layer and the third layer is independently 250 micrometers to 450 micrometers, and the thickness of the second layer is 50 micrometers to 250 micrometers.

2. The polymer film according to claim 1, characterized in that The first melt index and the third melt index are each independently 1.5 g / 10 min to 3.3 g / 10 min.

3. The polymer film according to claim 1, characterized in that The first melt index, the second melt index, and the third melt index are measured according to ASTM D1238 at 190° C. and a load of 2.16 kg.

4. The polymer film according to any one of claims 1 to 3, characterized in that The first layer, the second layer and the third layer each independently contain polyvinyl butyral.

5. The polymer film according to any one of claims 1 to 3, characterized in that The polyvinyl acetal contained in the second layer has an acetalization degree of 56 mol % to 74 mol %, an acetylation degree of 5 mol % to 15 mol %, and a hydroxyl content of 20 mol % to 30 mol %.

6. The polymer film according to any one of claims 1 to 3, characterized in that The polyvinyl acetal contained in the first layer and the third layer independently has an acetalization degree of 60 mol % to 75 mol %, an acetylation degree of 0.1 mol % to 5 mol %, and a hydroxyl content of 20 mol % to 35 mol %.

7. The polymer film according to any one of claims 1 to 3, characterized in that The polyvinyl acetal contained in the second layer has a number average molecular weight of 100,000 to 240,000.

8. The polymer film according to any one of claims 1 to 3, characterized in that The number average molecular weight of the polyvinyl acetal contained in the first layer and the third layer is independently 90,000 to 120,000.

9. A laminated glass, characterized in that: The glass substrate comprises a first glass sheet, an intermediate film and a second glass sheet in sequence, wherein the intermediate film is the polymer film according to any one of claims 1 to 3.

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