DE102010003316B4 - Thermoplastic mixture with low intrinsic color and high photothermal stability and PVB film produced therewith - Google Patents

Abstract

Thermoplastic mixture containing at least one polyvinyl acetal and at least one plasticizer, characterized by the addition of 0.001 to 1 wt .-% of at least one compound of formula 1 with n = 1 to 10 as a stabilizer.

Description

Technical area

The invention relates to mixtures of plasticized polyvinyl acetals or films extruded therefrom with low intrinsic color and high photothermal stability by using particularly suitable phenolic antioxidants.

State of the art

Like many other thermoplastics polyvinyl butyral is often equipped with phenolic antioxidants (phenolic AO), whose task is z. B. in the film extrusion caused by high processing temperatures radical cleavage reactions. As a result, the length of the polymer chains is kept substantially constant, so that the mechanical properties of the extruded material as a result of the extrusion process are not deteriorated.

However, many phenolic antioxidants have the disadvantage of causing yellowing, which is due to reaction products of the antioxidants, depending on the extrusion conditions. Even in a finished, already glued between two sheets of glass PVB film phenolic antioxidants under UV irradiation - especially at elevated temperature - subsequently cause yellowing, which is not only undesirable for aesthetic reasons, but also reduces the light transmission of the glass laminate over time ,

For example, the in WO 03/078160 A1 (Du Pont) yellowing of PVB sheet with the plasticizer 3G8 preferred binuclear phenolic antioxidants such as Lowinox ^® 22M46 and 44B25 as relatively strongly under UV irradiation.

Some antioxidants, such as BHT (CAS Reg No: 128-37-0), are UV stable, but relatively volatile due to their low molecular weight, so that in the non-glass-covered film material along the edge of the laminate a premature depletion of the antioxidant can take place and the polymer chains are no longer protected at these points of the film against chain degradation. In addition, BHT has the disadvantage that at elevated temperature and access of atmospheric oxygen intensely yellow colored reaction products can arise. This may manifest itself as a lack of use as laminated safety glass in the form of yellowing of the PVB film in the edge region of the laminate after the autoclave process.

Other phenolic antioxidants, like that from the EP 0188236 known alkylidene bis (benzotriazolyl phenol) are expensive to produce.

task

The object of the present invention was to identify a phenolic antioxidant suitable for the high requirements in the production of films of plasticized polyvinyl acetals by extrusion, which is suitable for optical applications, d. H. shows no yellowing on the laminated film, no unacceptable increase in yellowness in the extrusion and particularly good photothermal stability.

Solution of the task

Surprisingly, it has been found that by using oligomeric, sterically hindered phenols, films of plasticized polyvinyl acetal having a low intrinsic color and a particularly high photothermal stability can be obtained.

mit n = 1 bis 10 als Stabilisator bzw. hiermit hergestellte Folien.The present invention therefore thermoplastic mixtures containing at least one polyvinyl acetal and at least one plasticizer, characterized by the addition of 0.001 to 1 wt .-% of at least one compound of formula 1

with n = 1 to 10 as a stabilizer or films produced therewith.

Suitable stabilizers are those of CAS Reg. No. 68610-51-5. Compounds of this type are known as butylated reaction product of dicyclopentadiene and p-cresol, commercial products "Wingstay ^® L" from Eliokem or "Lowinox ^® CPL" Chemtura or "Ralox LC ^®" by the company Raschig available.

Mixtures or films according to the invention preferably contain 0.005-0.5% by weight, particularly preferably 0.01-0.25% by weight, in particular 0.02-0.1% by weight and most preferably 0.03-0 , 08 wt .-% of the oligomeric, sterically hindered phenols according to formula 1.

In addition to the use of the stabilizers according to formula 1, the adjustment of a small alkali titre of the mixture according to the invention z. B. in the neutralization of the polyvinyl acetal improved color and photothermal stability of the mixture or film of the invention.

The alkalititer is, as indicated in the examples, determined by neutralization of the mixture or film according to the invention with hydrochloric acid and is preferably between 2 and 70, in particular between 3 and 50 and most preferably between 5 and 30.

The adjustment of the alkali titre can be carried out by appropriate neutralization of the polyvinyl acetal during or after its production by acetalization of polyvinyl alcohol or by addition of metal salts to the mixture according to the invention. When using the films according to the invention for laminated glass laminates, the metal salts generally also function as anti-adhesion agents.

Particularly suitable for the blend according to the invention are polyvinyl acetals, available as acetalization products of polyvinyl alcohol PVA with butyraldehyde, d. H. Polyvinyl butyral (PVB). Mixtures according to the invention may contain one or more polyvinyl acetals which may differ in molecular weight, degree of acetalization, residual alcohol content or nature of the acetal group.

Mixtures or films according to the invention may comprise alkaline earth metal, zinc, aluminum or alkali metal ions as anti-adhesion agents. These are present in the mixture / film in the form of the salts of mono- or polyvalent inorganic or mono- or polybasic organic acids. Examples of counterions are z. As salts of organic carboxylic acids such as formates, acetates, trifluoroacetates, propionates, butyrates, benzoates, 2-ethylhexanoates, etc., preferably carboxylic acids having less than 10 carbon atoms, preferably less than 8, preferably less than 6, preferably less than 4 and most preferably used with less than 3 C atoms. Examples of inorganic counterions are chlorides, nitrates, sulfates, phosphates. Other counterions may be anions attributable to the surfactants, such as sulfonates or phosphates.

Furthermore, the stated favorable optical properties of the mixture according to the invention can be improved by selecting the polyvinyl alcohol (PVA) used to prepare the polyvinyl acetal. If unsaturated units in the polymer chain already exist at the level of the PVA as defects, they will inevitably be found again in the polyvinyl acetal produced therefrom and impair its light stability or UV transmission. The unsaturated moieties may be in the form of double bonds isolated or conjugated to each other or conjugated to carbonyl bonds. These unsaturated units can be detected by UV spectroscopy in PVA.

Very high levels of defects result in measurements of the PVA used in 4 wt .-% solution in H ₂ O to extinctions at 280 nm from near 1. For the production of polyvinyl acetal used in the invention therefore preferably polyvinyl alcohols are used, which in a 4 wt .-% aqueous solution at 280 nm absorbance values of less than 0.5, of less than 0.3, in particular 0.2 and preferably 0.1.

Because of their good photothermal inherent stability in particular the types Tinuvin ^® 328, 327 and 326 are suitable also as a UV absorber compounds benzotriazole type. The present invention expressly includes the use of benzotriazoles. Although films produced therewith have a higher inherent color, they also have particularly low delta b * values after irradiation testing.

Also in addition to the use of the phenolic antioxidants of Formula 1 and instead of or in addition to the above mentioned. Volatile antioxidants, the mixtures or films of the invention with one or more non-aromatic light stabilizers, in particular with 0.001 to 1 wt .-% (based on the film mixture) hindered amines of the type HAS / HALS / NOR-HALS (sterically hindered amino ethers) be equipped, which can achieve a further improvement of the photothermal stability.

mit R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 = nicht-aromatische Substituenten wie H, C1-C20 Alkyl, Hydroxyalkyl, Alkoxyalkyl, Acyloxyalkyl, jeweils unsubstituiert oder durch Aldehyd-, Keto- oder Epoxidgruppen substituiert
R12 = glatte Verbindung, C1-C20 Alkyl, Hydroxyalkyl, Alkoxyalkyl, Acyloxyalkyl, jeweils unsubstituiert oder durch Aldehyd-, Keto- oder Epoxidgruppen substituiert
n = 2–4
m = 1–10.Particularly suitable non-aromatic light stabilizers are sterically hindered amines of the general formulas II, III and / or IV

with R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 = non-aromatic substituents such as H, C1-C20 alkyl, hydroxyalkyl, alkoxyalkyl, acyloxyalkyl, in each case unsubstituted or by aldehyde, keto or epoxy groups substituted
R 12 = straight-chain compound, C 1 -C 20 -alkyl, hydroxyalkyl, alkoxyalkyl, acyloxyalkyl, in each case unsubstituted or substituted by aldehyde, keto or epoxide groups
n = 2-4
m = 1-10.

Compounds of this type are commercially available, are suitable, for example, Tinuvin ^® 123 (NOR-HALS), Tinuvin ^® 144, Tinuvin ^® 622, Tinuvin ^® 770 and the di-N-methylated derivative, of Messrs. Ciba Specialties. Are particularly well suited ADK Stab ^® LA-57, LA-52 and LA-62 from the company. Asahi Denka Co. or Uvinul ^® 4050 H from BASF AG.

In addition to the use of the phenolic antioxidants of Formula 1, the thermoplastic blends / films may contain a base stabilizer with another photostable phenolic antioxidant that is less suitable on its own due to other properties, such as high volatility. In the context of the present invention, this means antioxidants having an increased volatility under the conditions of extrusion and processing of PVB film, which generally applies to phenolic antioxidants having a molecular weight of less than 300 g / mol. These additional phenolic antioxidants may be used in place of or in combination with the HAS / HALS / NOR-HALS type hindered amines. The thermoplastic mixture or films according to the invention preferably contain phenolic antioxidants having a molecular weight of less than 300 g / mol in an amount of 0.001-0.25% by weight (based on the film mixture). Particularly suitable phenolic antioxidants are BHT (CAS Reg. No .: 128-37-0) or 4-tert-octylphenol (CAS Reg. No .: 140-66-9).

The oligomeric, sterically hindered phenolic antioxidants of the formula 1 and, if appropriate, the further antioxidants can be introduced in various ways into the mixture according to the invention or the film produced therewith. They can already be present in the polymer before the extrusion or added dissolved or suspended in the plasticizer during the extrusion or at the stage of the blend preparation. Preferably, the phenolic antioxidants are already introduced at the stage of PVB synthesis, z. B. by spraying onto the finished polymer particles or during the precipitation of the PVB polymer from the reaction solution. The same applies to the addition of sterically hindered amine light stabilizers, which are preferably added dissolved in the plasticizer.

The films preferably have a total plasticizer content d. H. the proportion of all plasticizers in the film in the range of 10-45 wt .-%, 14-36 wt .-%, 16-32 wt .-%, 18-30 wt .-%, in particular 22-28 wt .-% on. Films according to the invention or laminates bonded thereto may contain one or more plasticizers.

• – Ester von mehrwertigen aliphatischen oder aromatischen Säuren, z. B. Dialkyladipate wie Dihexyladipat, Dioctyladipat, Hexylcyclohexyladipat, Mischungen aus Heptyl- und Nonyladipaten, Diisononyladipat, Heptylnonyladipat sowie Ester der Adipinsäure mit cycloaliphatischen oder Etherbindungen enthaltenden Esteralkoholen, Dialkylsebazate wie Dibutylsebazat sowie Ester der Sebazinsäure mit cycloaliphatischen oder Etherbindungen enthaltenden Esteralkoholen, Estern der Phthalsäure wie Butylbenzylphthalat oder Bis-2-butoxyethylphthalat
• – Ester oder Ether von mehrwertigen aliphatischen oder aromatischen Alkoholen oder Oligoetherglykolen mit einem oder mehreren unverzweigten oder verzweigten aliphatischen oder aromatischen Substituenten, wie z. B. Estern von Di-, Tri- oder Tetraglykolen mit linearen oder verzweigten aliphatischen oder cycloaliphatischen Carbonsäuren; Als Beispiele für letztere Gruppe können dienen Diethylenglykol-bis-(2-ethylhexanoat), Triethylenglykol-bis-(2-ethylhexanoat), Triethylenglykol-bis-(2-ethylbutanoat), Tetraethylenglykol-bis-n-heptanoat, Triethylenglykol-bis-n-heptanoat, Triethylenglykol-bis-n-hexanoat, Tetraethylenglykoldimethylether und/oder Dipropylenglykolbenzoat
• – Phosphate mit aliphatischen oder aromatischen Esteralkoholen wie z. B. Tris(2-ethylhexyl)phosphat (TOF), Triethylphosphat, Diphenyl-2-ethylhexylphosphat, und/oder Trikresylphosphat
• – Ester der Zitronensäure, Bernsteinsäure und/oder Fumarsäure.

Basically suitable plasticizers for the mixtures or films according to the invention are one or more compounds selected from the following groups:

• Esters of polyhydric aliphatic or aromatic acids, e.g. As Dialkyladipate as Dihexyladipat, Dioctyladipat, Hexylcyclohexyladipat, mixtures of heptyl and nonyl adipates, Diisononyladipat, Heptylnonyladipat and esters of adipic acid with cycloaliphatic or ether-containing ester alcohols, dialkyl sebacates such as dibutyl sebacate and esters of sebacic acid with cycloaliphatic or ether bonds containing ester alcohols, esters of phthalic acid such as butyl benzyl phthalate or bis-2-butoxyethyl phthalate
• - Esters or ethers of polyhydric aliphatic or aromatic alcohols or Oligoetherglykolen with one or more unbranched or branched aliphatic or aromatic substituents, such as. B. esters of di-, tri- or tetraglycols with linear or branched aliphatic or cycloaliphatic carboxylic acids; As examples of the latter group may be used diethylene glycol bis (2-ethylhexanoate), triethylene glycol bis (2-ethylhexanoate), triethylene glycol bis (2-ethylbutanoate), tetraethylene glycol bis-n-heptanoate, triethylene glycol bis-n heptanoate, triethylene glycol bis-n-hexanoate, tetraethylene glycol dimethyl ether and / or dipropylene glycol zoate
• - Phosphates with aliphatic or aromatic ester alcohols such. Tris (2-ethylhexyl) phosphate (TOF), triethyl phosphate, diphenyl 2-ethylhexyl phosphate, and / or tricresyl phosphate
• - esters of citric acid, succinic acid and / or fumaric acid.

Suitable as plasticizers for the mixtures or films according to the invention are one or more compounds selected from the following group: di-2-ethylhexyl sebacate (DOS), di-2-ethylhexyl adipate (DOA), dihexyl adipate (DHA), dibutyl sebacate (DBS), triethylene glycol bis-n-heptanoate (3G7), tetraethylene glycol bis-n-heptanoate (4G7), triethylene glycol bis-2-ethylhexanoate (3GO or 3G8) tetraethylene glycol bis-n-2-ethylhexanoate (4GO or 4G8) di- 2-butoxyethyl adipate (DBEA), di-2-butoxyethoxyethyl adipate (DBEEA) di-2-butoxyethyl sebacate (DBES), di-2-ethylhexyl phthalate (DOP), di-isononyl phthalate (DINP) triethylene glycol bis-isononanoate, triethylene glycol bis-2 propylhexanoate, tris (2-ethylhexyl) phosphate (TOF), 1,2-cyclohexanedicarboxylic acid diisononyl ester (DINCH) and dipropylene glycol zoate.

Especially suitable are softening whose polarity expressed by the formula 100 × O / (C + H) is less than or equal to 9.4, where O, C and H are the number of oxygen, carbon and hydrogen atoms in the respective molecule stands. The following table shows plasticizers which can be used according to the invention and their polarity values according to the formula 100 × O / (C + H). Surname abbreviation 100 × O / (C + H) Di-2-ethylhexyl (DOS) 5.3 Di-isononyl (DINA) 5.3 1,2-cyclohexanedicarboxylate (DINCH) 5.4 Di-2-ethylhexyl (DOA) 6.3 dihexyladipate (DHA) 7.7 dibutyl (DBS) 7.7 Triethylene glycol-bis-2-propylhexanoat 8.6 Triethylene glycol-bis-i-nonanoate 8.6 Di-2-butoxyethylsebacat (DBES) 9.4 Triethylene glycol-bis-2-ethylhexanoate (3G8) 9.4

Furthermore, the mixtures or films according to the invention may additionally contain further additives, such as, for example, antistatics, fillers, IR-absorbing nanoparticles or chromophores, dyes, surface-active substances, pigments and adhesion regulators.

The basic preparation and composition of films based on polyvinyl acetals is z. In EP 185 863 B1 . EP 1 118 258 B1 WO 02/102591 A1 . EP 1 118 258 B1 or EP 387 148 B1 described.

Thermoplastic mixtures according to the invention can be extruded in a conventional manner at about 160 to 230 ° C to give film. Such films preferably have a DYI of less than 5, more preferably less than 4 and in particular less than 3 and a delta b * value of less than 3, preferably less than 2.5, more preferably less than 2 and in particular less than 1 , 5 on.

The films of the present invention can be used to make laminated glass laminates, windshields, or photovoltaic modules.

Testing and measuring methods:

The radiation resistance of the films was tested in the laminated glass between two glasses thickness 2 mm of the type Optiwhite ^® (iron oxide arm glass from Pilkington with compared to typical clear glass increased permeability for UV-A radiation). In this case, laminates measuring 15 × 15 cm in the irradiation chamber according to EN 12543 were laid out over a period of 20 weeks. Notwithstanding the requirements of EN 12543, a higher test temperature of 80 ° C has been set since this corresponds more to a combined radiation and temperature load actually occurring in an unfavorable case.

Comparative measurement of the b * value (CIELab) of the irradiated laminate against a dark-stored original laminate can easily be used to determine the relative increase in the b * value as a measure of the radiation resistance of the PVB film with the respective stabilizer type or the respective stabilizer combination. The measurement of the b * value was carried out on a colorimeter "ColorQuest XE" from the manufacturer Hunterlab in the CIELAb system in transmission (10 ° / D65). The delta b * value is the difference between the b * value of the irradiated sample and the b * value of the original sample.

For a better differentiation of the intrinsic color of the extruded film (without additional exposure to radiation), a laminated glass with 10 layers of foil in thickness 0.76 mm (total thickness 7.6 mm) with two panes of clear glass (2 mm Planilux ^® ) - on the ColorQuest XE measured by the following method. In the method, the inherent color of the glass is averaged out by measuring the pair of disks of the identical glass batch as a blank sample. The yellowness index (YI [D1925]) is calculated automatically according to Hunterlab 2 ° / C mode. The DYI value given in the example table is the difference between YI (laminate 10 × 0.76) - YI (glass pair).

The thermooxidative stability (edge stability) is evaluated on test laminates of 2 × 3 mm float glass measuring 15 × 15 cm. After a conventional Walzenvorverbundschritt the test laminates for the production of the final composite are subjected to a prolonged and hot autoclave process, which for a total duration of 6 h, a holding time of 3 h at 160 ° C and 12 bar. As a result of the thermo-oxidative stress and as a function of the selected stabilization variant, the film mass located at the edge of the test laminate discolors within a bandwidth of "not at all" to "dark amber". The former is assigned the grade 0, the latter the grade 6 with corresponding ratings in between.

The polyvinyl alcohol and polyvinyl alcohol acetate content of the polyvinyl acetals was determined according to ASTM D 1396-92. The analysis of the metal ion content was carried out by atomic absorption spectroscopy (AAS). The water or moisture content of the films is determined by the Karl Fischer method.

To determine the UV absorption of the polyvinyl alcohol used in the acetalization this is in a UV / VIS spectrometer, z. Perkin-Elmer Lambda 910, as a 4% aqueous solution in a Measure layer thickness of 1 cm at the wavelength 280 nm. The measured value should be based on the dry matter content of the PVA.

Examples

3G8

Triethylenglykol-bis-2-ethylhexanoat

DBEA

Bis-(2-butoxyethyl)adipat

DINCH

1,2-Cyclohexandicarbonsäurediisononylester

DINA

Di-isononyladipat

PVB

Polyvinylbutyral mit dem angegebenen PVA-Gehalt

Lowinox^® 22M46

zweikerniges phenolisches AO (Chemtura)

Lowinox^® 44B25

zweikerniges phenolisches AO (Chemtura)

Lowinox^® CPL

oligomeres AO CAS 68610-51-5 (Chemtura)

BHT

Verbindung der CAS 128-37-0

It means

3G8

Triethylene glycol-bis-2-ethylhexanoate

DBEA

adipate bis- (2-butoxyethyl)

DINCH

1,2-cyclohexanedicarboxylate

DINA

Di-isononyl

PVB

Polyvinyl butyral with the stated PVA content

Lowinox ^® 22M46

dinuclear phenolic AO (Chemtura)

Lowinox ^® 44B25

dinuclear phenolic AO (Chemtura)

Lowinox ^® CPL

oligomeric AO CAS 68610-51-5 (Chemtura)

BHT

Connection of the CAS 128-37-0

It has been found that films according to the invention have a low intrinsic color and a minimal tendency to yellow and scarcely stain under oxidative conditions (extended autoclave process at 160 ° C.).

Comparative Example 1 shows that when using about 220 ppm BHT as the sole stabilizer, a film with low intrinsic color (low DYI) can be obtained, which, however, has a strong edge discoloration under thermo-oxidative conditions.

Comparative Examples 2-5 show that with the additional use of the dodecaholic Lowinox ^® 22M46 or 44B25 phenolic antioxidants, the thermooxidative stability can be improved while the film color is acceptable at the same time, but the radiation resistance to VG 1 is worsened.

Inventive Examples 1 and 2 show that with additional use of the oligomeric antioxidant Lowinox ^® CPL a film of low intrinsic color and good thermo-oxidative stability and low yellowing tendency can be obtained under UV irradiation.

Comparative Example 6 shows that when using about 580 ppm BHT as the sole stabilizer, a film with low intrinsic color (low DYI) can be obtained, which, however, has a strong edge discoloration under thermo-oxidative conditions.

Comparative Examples 7-8 show that when using the binuclear phenolic antioxidant Lowinox ^® 22M46 been improved as the sole stabilizer, the thermooxidative stability to VG 6, however, both intrinsic film color and radiation resistance are insufficient.

Comparative Examples 9-12 show that improved significantly when using the binuclear phenolic antioxidant Lowinox ^® 44B25 as the sole stabilizer, the thermooxidative stability to VG 6, and no significant degradation of the film intrinsic color occurs, however, the irradiation resistance is deteriorated with increasing concentration.

Inventive Examples 3-5 show that when using the oligomeric antioxidant Lowinox ^® CPL in combination with the HALS ADEKA STAB ^® LA 57 from the company Adeka Palmarole a film of low intrinsic color and good thermooxidative stability and particularly low yellowing tendency can be obtained under UV irradiation ,

Inventive Examples 6-8 show that can be obtained with the use of the oligomeric antioxidant Lowinox ^® CPL in combination with the HALS Uvinul ^® 4077 from BASF SE, a film of low inherent color and good thermooxidative stability, especially low tendency to yellowing under UV radiation.

Inventive Examples 9-11 show that when using the oligomeric antioxidant Lowinox ^® CPL to stabilize a higher acetalized PVB, which is plasticized with the low-polar plasticizers DINCH or DINA, a film of low intrinsic color and good thermal oxidative stability and low yellowing tendency under UV Radiation.

Inventive Examples 12-14 show that when using the oligomeric antioxidant Lowinox ^® CPL to stabilize a higher acetalized PVB, which is softened with the less polar plasticizers DINCH or DINA, with the additional use of sterically hindered amines as a light stabilizer a film of low intrinsic color and good thermo-oxidative stability and particularly low yellowing tendency under UV irradiation.

Claims (7)

Thermoplastic mixture containing at least one polyvinyl acetal and at least one plasticizer, characterized by the addition of 0.001 to 1 wt .-% of at least one compound according to formula 1

with n = 1 to 10 as stabilizer. Thermoplastic mixture according to claim 1, characterized in that the mixture additionally contains 0.001 to 1 wt .-% of non-aromatic light stabilizers of HAS / HALS / NOR-HALS type. Thermoplastic mixture according to claim 1 or 2, characterized in that the mixture additionally contains phenolic antioxidants having a molecular weight of less than 300 g / mol in an amount of 0.001-0.25 wt .-%. Film produced from a thermoplastic mixture according to claims 1 to 3. A film according to claim 4, characterized in that the film has a delta b * value of less than 3. A film according to claim 5, characterized in that the film has an intrinsic color DYI of less than 5. Use of the film according to claims 4 to 6 for the production of laminated glass laminates, windshields or photovoltaic modules.