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CN-122029047-A - Polyvinyl acetal film with improved stiffness

CN122029047ACN 122029047 ACN122029047 ACN 122029047ACN-122029047-A

Abstract

The present invention relates to a polyvinyl acetal film with improved shear relaxation modulus comprising a reduced amount of plasticizer.

Inventors

  • M. HESS
  • I. Stezel

Assignees

  • 可乐丽欧洲有限责任公司

Dates

Publication Date
20260512
Application Date
20241029
Priority Date
20231114

Claims (10)

  1. 1. A polyvinyl acetal film comprising at least one plasticizer, wherein, A. The total amount of plasticizer in the polyvinyl acetal film is 13.0 to 16.0 wt%, B. a weight average molecular weight (Mw) of 170,000g/mol or higher as measured by GPC in tetrahydrofuran according to the method described in the specification, C. The shear relaxation modulus measured at 30 ℃ and 5min is higher than 5MPa.
  2. 2. The polyvinyl acetal film according to claim 1, wherein a total amount of plasticizers in the polyvinyl acetal film is 13.5 to 15.5 wt%.
  3. 3. The polyvinyl acetal film according to claim 1 or 2, wherein a weight average molecular weight (Mw) measured by GPC in tetrahydrofuran according to a method described in the specification is equal to or higher than 200,000g/mol.
  4. 4. The polyvinyl acetal film according to any of the preceding claims, wherein the polyvinyl acetal film has a yellowness index dYID of less than 2.0 measured according to the method described in the specification.
  5. 5. The polyvinyl acetal film according to any of the preceding claims, wherein the shear relaxation modulus measured at 20 ℃ and 12h is above 10MPa.
  6. 6. The polyvinyl acetal film according to any of the preceding claims, wherein the shear relaxation modulus measured at 35 ℃ and 3s is above 15MPa.
  7. 7. The polyvinyl acetal film according to any of the preceding claims, wherein the post-fracture behaviour determined according to EN 1288-3 at 23 ℃ and in a bending test as described in the specification is equal to or greater than 10min.
  8. 8. The polyvinyl acetal film according to any of the preceding claims, wherein the width of edge whitening from the edge of the laminate, determined in a test according to DIN EN ISO 9227 and as described in the specification, is equal to or less than 1mm.
  9. 9. A laminate comprising the polyvinyl acetal film according to any one of claims 1 to 8 sandwiched between two sheets of glass.
  10. 10. Use of the laminate according to claim 9 for the production of structural glass articles in glass floors and stairways, curtain walls or retaining wall glass articles.

Description

Polyvinyl acetal film with improved stiffness The present invention relates to a polyvinyl acetal film with improved shear relaxation modulus comprising a reduced amount of plasticizer. Interlayer films comprising polyvinyl acetals have long been known as adhesive layers for laminated glass. In particular, plasticized polyvinyl butyral (PVB) films are widely used as adhesive layers for glass-glass laminates, for example, for architectural applications such as architectural windows. Glass is increasingly being used in today's construction. Large scale glass facades play a key role here. Structural glass articles differ from conventional glass facades in their appearance and construction. The individual glass elements are separated from each other only by thin shadow gaps or silicone joints. The entire facade itself presents a smooth surface without discontinuities. The insulating glass or the retaining wall element is not held in place by glazing beads (glazing beads) or cover profiles. In such structural glazing applications, the strength, toughness and elasticity of the PVB interlayer film used in the glass laminate is of great importance, as the glass itself must withstand the loading of the facade. In the event of breakage of laminated safety glass in such applications, the interlayer alone needs to be sufficiently rigid to maintain the structural integrity of the element and to prevent serious accidents, i.e. it needs to possess good so-called "post-glass breakage properties". In this context, determination (Glass in building - Laminated glass and laminated safety glass - Determination of interlayer viscoelastic properties) of the viscoelastic properties of glass-laminated glass and laminated safety glass-interlayers in the european standard EN 16613:2019 "building defines certain load durations and temperature ranges, which show that the temperature range between 0 ℃ and 40 ℃ is particularly important for european building applications. In order to meet such criteria, it would be advantageous to have a high stiffness polyvinyl acetal film in this temperature range, for example represented by an improved high shear relaxation modulus G (t). In order to increase the rigidity of the polyvinyl acetal film, the amount of plasticizer used can be reduced. To this end, trosifol (r) Extra Stiff and Saflex TM DG41 PVB interlayer films with reduced amounts of plasticizer (as compared to conventional PVB sheet products) are commercially available. These products are more rigid than conventional PVB films and are therefore widely used in structural glass articles. US 10,889,087 B2 reports that for Saflex TM DG41 the plasticizer content is 20 parts per 100 parts resin, which corresponds to about 17 wt%. For certain applications in structural glass articles, an even more rigid interlayer film is required. However, further reduction of the amount of plasticizer also increases the melt viscosity of the polyvinyl acetal/plasticizer composition typically used in melt extrusion processes for making interlayer films. This increase in viscosity results in higher back pressure and shear forces, i.e., in more severe conditions in the extruder. These severe conditions lead to partial deterioration of the polyvinyl acetal and thus to an increase in the yellowness of the product, which is unacceptable for the appearance of glass facades. Thus, US 10,889,087 B2 teaches that further reduction of the plasticizer contained in the polyvinyl acetal would render its processing unacceptable. In contrast, this patent proposes the use of polyvinyl acetals with low molecular weights to reduce the viscosity in the melt extrusion step. However, the use of such low molecular weight polyvinyl acetals is generally associated with a decrease in creep resistance, in particular above the glass transition temperature Tg. Thus, there remains a need in the industry for a method of producing a polyvinyl acetal interlayer film having both a high shear modulus G (t) over a significant temperature range and simultaneously acceptable optical quality, as measured, for example, by its yellowness index and processability. It is therefore an object of the present invention to provide a film with improved properties, wherein the improvement comprises higher stiffness, higher shear relaxation and/or shear storage modulus, improved processability, lower manufacturing costs and/or higher optical quality, especially in terms of less haze and/or less yellowness. The present invention has solved these and other problems. In a first aspect, the present invention relates to a polyvinyl acetal film comprising at least one plasticizer, wherein, A. the total amount of plasticizer in the polyvinyl acetal film is 13.0 to 16.0 wt%, B. a weight average molecular weight (Mw) of 170,000g/mol or more as measured by GPC in tetrahydrofuran according to the method described below, C. The shear relaxation modulus measured at 30 ℃ and 5min is higher than 5MPa. Brief description of t