JPH04345604A - Terpolymer excellent in adhesiveness and transparency and its production - Google Patents

Abstract

PURPOSE:To develop an ethylene/vinyl acetate/vinyl alcohol terpolymer which can be laminated with glass by short-time hot pressing. CONSTITUTION:An ethylene/vinyl acetate/vinyl alcohol terpolymer having a content of vinyl alcohol units of 15.6wt.% or above and a content of units derived from vinyl acetate of 20wt.% or above prepared by saponifying an ethylene/vinyl acetate bipolymer having a content of units derived from vinyl acetate of 46-55wt.% and an MFR of 1-100g/10min; or a terpolymer prepared by crosslinking the above terpolymer. The former terpolymer can be laminated with glass by short-time hot pressing without autoclaving while keeping its optical properties and strengths as high as those of conventional intermediate layers of laminated glass. Its strength is further improved by crosslinking.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a terpolymer with excellent adhesiveness and optical properties, and a method for producing the same, and more specifically to an ethylene/vinyl acetate/vinyl alcohol terpolymer or The present invention relates to a terpolymer which is obtained by crosslinking the terpolymer and has excellent adhesiveness, optical properties and strength, and a method for producing the same. This terpolymer or a crosslinked product of the terpolymer exhibits extremely high performance as an intermediate layer of laminated glass (laminated glass) and the like.

0002

BACKGROUND OF THE INVENTION In recent years, as the safety level of automobiles has improved, safety measures for windshields have become absolutely essential to ensure the safety of passengers. the current,
There are extremely strict standards for safety glass used in automobile windshields, for example, in Japan, JAS
It is stipulated in the O standard. Satisfying this standard while also meeting cost requirements is an extremely difficult proposition for both glass and adhesives.

Up to now, polyvinyl butyral has been used almost exclusively as the material for the interlayer of laminated automotive glass. This laminated glass is characterized by its excellent transparency and high penetration resistance, but the performance of polyvinyl butyral as an intermediate layer material of laminated glass is not necessarily satisfactory. In other words,
When laminating with glass, it is highly hygroscopic, so it requires conditioning in advance, and it must be laminated one sheet at a time to the glass, and is placed in an autoclave under pressure for 30 minutes or more.
It is necessary to heat the glass for about two hours, which makes the manufacturing process of laminated glass very complicated.

[0004] Ethylene/vinyl acetate/vinyl alcohol terpolymer (EVAVAL) is an intermediate layer material that can be used for laminated glass and/or transparent synthetic resin plates, and has excellent low-temperature properties. known to be a material.

For example, US Pat. No. 4,137,364
The specification states that the vinyl acetate unit content is 40 to 60 wt%.
Disclosed is an adhesive film that is crosslinked by heating EVAVAL having an OH content of 1 to 6 wt% obtained by saponifying an ethylene/vinyl acetate copolymer in the presence of an electron beam or a specific crosslinking agent. ing.

[0006]

[Problems to be Solved by the Invention] The present inventors have discovered that while maintaining the optical properties and strength of the interlayer material of conventional laminated glass, the adhesiveness with various substrates including glass has been significantly improved, and the material can be used in autoclave. The purpose of this project is to develop an intermediate layer material that can be bonded to glass by thermocompression bonding in a short time of about 10 to 30 minutes without the use of EVAVAL, and which can greatly simplify the manufacturing process of laminated glass. After repeated studies focusing on the fact that adhesion with various substrates including glass increases as the vinyl alcohol unit content increases, we discovered that this is possible with EVAVAL within a specific composition range. invention has been achieved.

[0007]

[Means for Solving the Problems] That is, the present invention provides a method in which the content of units derived from vinyl acetate is 46 to 55 wt%, M
FR is 1-100g/10min (However, MFR is 190℃
, is the melt flow rate measured under a load of 2.16 kg. ) is homogeneously partially saponified, and the content of vinyl alcohol units is 15.
．． 6 wt% or more, and the content of units derived from vinyl acetate is 20 wt% or more.
A terpolymer of vinyl alcohol with excellent adhesiveness and transparency, and a content of units derived from vinyl acetate of 46 to 55 wt%, MFR
is 1 to 100g/10 minutes (however, MFR is 190℃, 2
．． This is the melt flow rate measured under a load of 16 kg. ) was homogeneously partially saponified, and the content of vinyl alcohol units was 15.6.
An ethylene-vinyl acetate-vinyl alcohol terpolymer having a content of units derived from vinyl acetate of 20 wt% or more by weight and excellent in adhesiveness and transparency. The method for producing the original copolymer, further including a content of units derived from vinyl acetate of 46 to 55 wt%,
MFR is 1 to 100 g/10 minutes (However, MFR is 190
It is a melt flow rate measured at ℃ and 2.16 kg load. ) is uniformly partially saponified to reduce the vinyl alcohol unit content to 1.
An ethylene-vinyl acetate-vinyl alcohol terpolymer having a content of 5.6 wt% or more and a content of units derived from vinyl acetate of 20 wt% or more, and after forming this into a sheet form, subjecting it to ionizing radiation or crosslinking. The present invention relates to a method for producing a terpolymer having excellent adhesiveness and transparency, which is characterized by crosslinking with an agent.

As mentioned above, the composition of the ethylene/vinyl acetate binary copolymer used in the present invention is determined by (1) the content of units derived from vinyl acetate in the copolymer, and (2) the melt flow rate (MFR). stipulated.

[0009] Here, the content of units derived from vinyl acetate (vinyl acetate units) in the copolymer is 46 to 55 wt.
%, preferably 48 to 53 wt%. When a copolymer containing less than 46 wt % of vinyl acetate units is used as a starting material, the resulting terpolymer cannot achieve the object of the present invention from two viewpoints. One of them is that when processing is performed with emphasis on transparency, the strength becomes insufficient, and when laminated with glass or synthetic resin, the penetration resistance becomes insufficient. Another problem is that high transparency cannot be maintained over a wide temperature range when strength is emphasized. In any case, strength and transparency are contradictory requirements, and both cannot be fully satisfied over a wide temperature range.

On the other hand, the vinyl acetate unit content is 55 wt%
In general, a terpolymer that satisfies haze properties can be easily obtained, but penetration resistance cannot be maintained and it is difficult to achieve both.

The MFR (measured at 190°C and a load of 2.16 kg) of this ethylene/vinyl acetate binary copolymer is 1 to 1.
100g/10 minutes, preferably 2 to 50g/10
It's a minute. The MFR of the binary copolymer as a starting material has a very large effect on the impact strength of the terpolymer obtained from the binary copolymer or its crosslinked product. MFR is 1
If it exceeds 00 g/10 minutes, the penetration resistance of the crosslinked terpolymer (EVAVAL) obtained by partial saponification of this product will decrease, regardless of the haze properties. On the other hand, MF
Penetration resistance improves when R is 1 g/10 minutes or less, but
Haze properties deteriorate.

The above-mentioned ethylene/vinyl acetate binary copolymer can be produced by a high-pressure copolymerization method or a solution copolymerization method, but one produced by a high-pressure copolymerization method is preferable. Particular preference is given to copolymers produced under a pressure of /cm2.

The terpolymer of the present invention can be obtained by uniformly partially saponifying an ethylene/vinyl acetate binary copolymer having the above properties. The degree of this saponification is
The content of units derived from vinyl alcohol is 15.6w
The range should be t% or more. If the vinyl alcohol unit content is less than 15.6 wt%, the lamination process with glass is complicated because it requires long-term or high-temperature adhesion in order to obtain sufficient adhesion with glass. becomes. In addition, although it is possible to satisfy haze characteristics, it is only possible to obtain results that are insufficient in terms of strength.

Furthermore, in order to obtain sufficiently satisfactory results regarding haze properties, it is necessary that the content of units derived from vinyl acetate be 20 wt % or more. If the content of units derived from vinyl acetate is less than 20 wt%, haze characteristics cannot be satisfied, and an optically satisfactory copolymer cannot be obtained.

This terpolymer has the above-mentioned properties, and various methods can be used to saponify it, but preferably the binary copolymer is partially saponified in a homogeneous solution state in the presence of a solvent. It can be obtained by saponification. Typical examples of this saponification method include a hydrolysis method or a transesterification method in the presence of an acid or alkali catalyst. For example, it consists of a good solvent and alcohol for both the binary copolymer as the starting material and the EVAVAL to be produced,
By carrying out the transesterification reaction using an acid or an alkali as a catalyst in a mixed solvent that dissolves both copolymers, uniform partial saponification can be achieved relatively easily.

In order to obtain the terpolymer having excellent optical properties of the present invention, the ethylene/vinyl acetate binary copolymer used for saponification and the terpolymer produced by partial saponification must be It is important that both are maintained in a homogeneous solution state during the saponification reaction. If the saponification reaction is carried out in a non-uniform state, the resulting terpolymer will be structurally non-uniform, making it difficult to achieve both optical properties and strength, especially when crosslinked.

The terpolymer thus obtained (E
VAVAL) has high adhesion to base materials such as glass,
When manufacturing laminated glass, short time and low lamination temperature can be used as lamination conditions with glass, and although it is flexible, it has high breaking strength, 200 kg/cm2
It shows high breaking strength. In addition, it is characterized by little variation in optical properties over a wide temperature range, with temperatures ranging from 20 to 130
The haze value is 1% or less in the temperature range of °C. The characteristics of such terpolymers are that they not only have excellent strength and optical properties even if they are non-crosslinked, but also contain a high amount of units derived from vinyl alcohol, so they can be used for glass and/or It is extremely useful as an intermediate layer (interlayer film) material for a transparent laminate sandwiched between a plurality of transparent plates made of synthetic resin plates. In particular, it is useful as an intermediate layer material for a laminate made of glass and synthetic resin, or synthetic resin and synthetic resin, which are not required to have very strict heat resistance.

If the terpolymer (EVAVAL) of the present invention is further crosslinked if necessary, it can be made to have even better strength while retaining its excellent optical properties. This crosslinking can be achieved by irradiating the terpolymer with ionizing radiation (electron beam, γ-ray, X-ray, etc.) or by irradiating the terpolymer with
Bis-tertiary-butyl-peroxy-3,3,5-trimethylcyclohexane, 2,5-dimethylhexane-2
, 5-dihydroperoxide, 2,5-dimethyl-
Crosslinking is carried out by adding and reacting a crosslinking agent such as 2,5-di-tert-butylperoxyhexane or benzoyl peroxide. In particular, it is preferable to crosslink the terpolymer by irradiating it with ionizing radiation such as an electron beam. Further, the degree of crosslinking is not particularly limited and may be appropriately selected depending on various circumstances such as the purpose of use and the shape of the crosslinked product. For example, when a crosslinked sheet of a terpolymer is applied to an intermediate layer of laminated glass for automobiles, it is preferably crosslinked so that the gel fraction is 45 wt% or more. Here, the gel fraction is a value obtained by performing Soxhlet extraction with boiling toluene for 5 hours. When the gel fraction is less than 45 wt%, shape retention is low when heated above the melting point, and there is no substantial meaning in crosslinking. In particular, for laminated glass that requires precise precision, it is difficult to achieve thickness accuracy during lamination, so the intermediate layer must have a gel fraction above a certain level, but 45 wt% or more is sufficient. be.

Furthermore, the crosslinked terpolymer thus obtained has excellent optical properties, but specifically, the haze value measured in the temperature range of 20 to 130°C is at most 1%, preferably 0.7% or less. A crosslinked product with a haze value exceeding 1% is not preferable since it reflects light from the outside, considering that it will be laminated with glass and used as a safety glass for the windshield of an automobile. Further, in order to obtain a crosslinked body with excellent penetration resistance, it is desirable that the tensile strength at break is 200 Kg/cm2 or more, and particularly preferably 250 Kg/cm2 or more.

When producing such a crosslinked product, the terpolymer is preferably processed into a sheet by conventional extrusion molding means prior to crosslinking. The molding temperature here is usually 60 to 150°C, but 80 to 13°C.
0°C is preferred.

[0021] Such a crosslinked sheet is produced by crosslinking the terpolymer by irradiating it with ionizing radiation such as an electron beam after forming the terpolymer into a sheet using ordinary extrusion means or simultaneously with sheet forming. It can be obtained by The thickness of the sheet is usually 0.2 to 1.0 mm.
It is.

The irradiation dose of ionizing radiation is expressed as a function of irradiation time, and the required irradiation dose here is 5 to 3
0 Mrad, and around 20 Mrad is most suitable. Below 5 Mrad, the effect of crosslinking does not appear, and at 30 Mrad
Irradiation for more than d causes problems in physical properties and economy, such as a decrease in the strength of the copolymer, an increase in irradiation time, and an increase in power consumption.

[0023] In the equipment used for crosslinking, such as an electron beam irradiation equipment, the accelerating voltage is 100 to 1,000 kV, and depending on the thickness of the sheet, the accelerating voltage is 300 to 900 kV in order to uniformly promote crosslinking to the inside. is preferred.

[0024]

[Examples] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. (Examples 1 to 3) (1) Preparation of ethylene/vinyl acetate/vinyl alcohol terpolymer Ethylene/vinyl acetate copolymer (EVA) with a vinyl acetate unit content of 52 wt% [Mw/Mn=2.7 , comonomer distribution (triad EEE fraction) = 42.0 mol%
. The solution was added gradually at a rate that did not cause precipitation of the copolymer.

The reaction was continued for 3 hours at the boiling point of the mixed solvent,
After the reaction was completed, acetic acid was added to the reaction mixture in an amount of 1.1 times the mole of sodium hydroxide used, and stirring was continued for 10 minutes. A small amount of water was added to the reaction solution, and the reaction solution was cooled to 40° C., and then an equal volume of acetone to the solution was added to precipitate the polymer while stirring the reaction solution well. After filtering out the precipitated powdery polymer, acetone/water mixed solvent (
The mixture was thoroughly washed at a volume ratio of 6/1) and dried under reduced pressure under heat to obtain a solvent-free ethylene/vinyl acetate/vinyl alcohol terpolymer (EVAVAL). Analysis and physical property measurements of the obtained terpolymer revealed the following properties. (a) Weight ratio of each unit of ethylene/vinyl acetate/vinyl alcohol = 55.5/28.2/16.3 (measured by infrared absorption analysis) (b) Tensile strength at break = 265 kg/cm2

002
6] (2) Creation of terpolymer sheet and crosslinked terpolymer sheet EVAVAL obtained as above was heated and compressed at 120°C using a mold whose surface was coated with Teflon. A terpolymer sheet with a thickness of 0.76 mm was produced by compression molding under a pressure of 20 kg/cm2. Next, using an electron beam irradiation device (manufactured by Nissin High Voltage Co., Ltd., scanning type, EPS750 type), the sheet is exposed to an electron beam in the air at an accelerating voltage of 750 kV to a predetermined irradiation dose. A crosslinked terpolymer sheet was prepared by irradiation. Table 1 shows the analysis results and physical property measurement results of the terpolymer sheet and crosslinked terpolymer sheet. As is clear from Table 1, the terpolymer of the present invention and its electron beam crosslinked product exhibit high breaking strength and stably maintain high transparency over a wide temperature range.

(Application Examples 1 to 4) Using the terpolymer sheet produced in Example 1 and the crosslinked sheet produced in Examples 1 to 3, a laminated glass (laminated glass) using these as an intermediate layer was produced. were prepared and their physical properties were measured. i.e. 2m thick
The terpolymer sheet prepared in the above example or its crosslinked sheet is sandwiched between two pieces of glass of m, and the surface temperature is 1.
Using a pressure press set at 20° C., lamination was performed by heating at a pressure of 20 kg/cm 2 for 10 minutes to create a laminated glass. The laminated glass created in this way is
A penetration test was conducted in accordance with SR 3212. As a result, each of these laminated glasses has a length of 5 m.
passed the penetration resistance test. Further, the amount of glass peeled at that time is shown in Table 2 for the laminated glasses using the crosslinked sheets manufactured in Examples 1 to 3, respectively. Also,
The physical properties of these laminated glasses are shown in Table 2.

(Examples 4 to 7) A terpolymer sheet and a crosslinked sheet thereof were prepared in the same manner as in Examples 1 to 3 above, except that the conditions shown in Table 1 were used. The analysis results of this product are shown in Table 1.

(Application Examples 5 to 12) Using the terpolymer sheets and crosslinked sheets thereof produced in Examples 4 to 7 above, a laminated glass having this as an intermediate layer was produced according to Application Examples 1 to 12 above.
It was prepared in the same manner as in 4 and its physical properties were measured. The results are shown in Table 2.

[0030]

[Table 1]

[0031]

[Table 2]

(Comparative Examples 1 to 5) Sheets of ethylene/vinyl acetate/vinyl alcohol terpolymer having properties outside the range of the present invention as shown in Table 3 and electron beam irradiated sheets thereof were prepared in the same manner as in the above examples. This was used to create a laminated glass in the same manner as in the above application example. These physical properties are shown in Table 4. As is clear from this table, when the vinyl alcohol content in the terpolymer is below the range of the present invention, when laminating it with glass, the same amount as the terpolymer within the scope of the present invention is used. Under the lamination conditions, it is clear that the adhesion to the glass is insufficient, and when a penetration resistance test is conducted, the results are poor, and the amount of glass peeled off during the test is large. If we consider these lamination conditions, such as increasing the temperature and lengthening the lamination time, the adhesion to the glass will improve and the amount of glass peeling during the test will decrease, but the strength will be low. Penetration resistance does not improve.

[0033]

[Table 3]

[0034]

[Table 4]

These Examples and Comparative Examples show that the copolymer of the present invention exhibits sufficient adhesive strength with glass when laminated for a short time and at low temperatures, and has excellent optical properties and penetration resistance. It's obvious.

[0036]

[Effects of the Invention] The ethylene-vinyl acetate-vinyl alcohol terpolymer of the present invention can be bonded to various base materials by short-term thermal bonding without using an autoclave, and has excellent strength. It maintains excellent optical properties such as transparency over a wide temperature range, and can be applied to interlayers such as laminated glass and laminated transparent plastics (acrylic resin, polycarbonate resin, etc.) for safety purposes such as automobile windshields. Effectively used as glass or its substitute. In addition, the crosslinked product of this terpolymer has excellent optical properties over a wide temperature range and further improved mechanical strength, making it suitable for laminated glass.
It is particularly effectively used as an intermediate layer.

Claims (5)

[Claims] Claim 1: The content of units derived from vinyl acetate is 46 to 55 wt%, and the MFR is 1 to 100 g/10 minutes (However, MFR is the melt flow rate measured at 190°C and a load of 2.16 kg.) The ethylene-vinyl acetate binary copolymer is homogeneously partially saponified, and the content of vinyl alcohol units is 15.6 wt% or more, and the content of units derived from vinyl acetate is 20 wt% or more. - A terpolymer with excellent adhesiveness and transparency, characterized by being a vinyl acetate-vinyl alcohol terpolymer. 2. The ethylene-vinyl acetate-vinyl alcohol terpolymer according to claim 1, having a gel fraction of 45 wt.
A ternary copolymer with excellent adhesiveness and transparency that is cross-linked to more than %. 3. The content of units derived from vinyl acetate is 46 to 55 wt%, and the MFR is 1 to 100 g/10 minutes (However, MFR is the melt flow rate measured at 190° C. and a load of 2.16 kg.) The ethylene-vinyl acetate binary copolymer is uniformly partially saponified, and the content of vinyl alcohol units is 15.6 wt% or more, and the content of units derived from vinyl acetate is 20 wt% or more. - A method for producing a terpolymer with excellent adhesiveness and transparency, characterized in that it is a vinyl acetate-vinyl alcohol terpolymer. 4. The content of units derived from vinyl acetate is 46 to 55 wt%, and the MFR is 1 to 100 g/10 minutes (However, MFR is the melt flow rate measured at 190° C. and a load of 2.16 kg.) The ethylene-vinyl acetate binary copolymer is homogeneously partially saponified, and the content of vinyl alcohol units is 15.6 wt% or more, and the content of units derived from vinyl acetate is 20 wt% or more. - A method for producing a terpolymer with excellent adhesiveness and transparency, which comprises using a vinyl acetate-vinyl alcohol terpolymer and crosslinking this with ionizing radiation or a crosslinking agent. 5. The method for producing a terpolymer having excellent adhesiveness and transparency according to claim 4, wherein the ionizing radiation is an electron beam and the irradiation dose is 5 to 30 Mrad.