FI81369B - PLAST MED STOR UV PERMEABILITET, OCH FOERFARANDE FOER DESS FRAMSTAELLNING. - Google Patents

Description

1 81369

Plastic with high UV transmittance and its manufacturing method. - Plastic with a UV permeability, which can be further reduced.

The invention relates to a methyl imetacrylate-based plastic having a permanent and high radiation transmittance in the UV range, and to a process for its production. The invention further relates to the technical use of plastic in a solarium or as a UV-permeable coating.

EP-B 16 870 already discloses methyl imetacrylate-based plastics with high UV-A (300-400 nm) and UV-B (260-320 nm) transmittances. High UV transmittance is maintained even under the influence of radiation for a longer time when the plastic contains a small amount of sterically hindered amine of the formula

R

f-j-R

A -R '

I - R

wherein R represents the same or different alkyl groups, R 'is a hydrogen atom or an alkyl group and A is an optionally substituted 2- or 3-membered alkylene chain. When methyl methacrylate-based plastics have a UV transmittance decreasing from about 80 ° C to 12 ° C within an irradiation time of 1000 hours, plastics containing said sterically hindered amine still have a transmittance of 50% after an equally long irradiation time. When a further 12% acrylic ester, such as methyl acrylate, is used in the formation of the plastic in addition to methyl methacrylate, no reduction in UV transmittance can be observed with plastics containing said sterically hindered amine for a period of 1000 hours.

It has now been found that the permeability of methyl imetacrylic-based 2 81369 plastics containing 0.01 to 1% by weight of said sterically hindered amine even further increases under UV irradiation for a long time and again does not decrease even with an irradiation time of 4000 hours when the plastic contains 1 -10% by weight of an aliphatic plasticizer compatible with polymethyl methacrylate, boiling above 120 ° C. Preferred properties are shown in the following Table 1: 3 81 369

9 S

c <D o 'T o r-' ui (n tn ro CO 00 03 CD CD CO 03 O 3 O: (0

ΓΛ, rO

§ (- ^ UQ f- 3 (N -h CO (N

03 C r— C— Γ- CO CO CD Γ ~ ro. «“ MIC i • CD>,: => 03 • H>, 3

E 3 M C

. _j a)> »ω,, en 3 cd uoromeoeotNuo cn; 1 h Cocor-cocococo »h CO C: tö 3 3 C-C 03 p. 3: co 3 e: to m ό fl \ r ~ (“H 4-1

'' t- I CMC r-cor-rocN-uco CN

s? in o r-r-r-cocDCDt- · ro ia 3 3 e

VO C

- co °° 03

VO * H

- CO CS -H

~ -u CS 4-Ϊ

^ CO

• H CO

UH- | \ • h>, (0 (0 o o o o o o g g h ^ (h ooooogg. G

, m Ή -HD OOOOOOO O

Λ 03 CD C

° D O 3 ro τΓ ^ O rl ^ -h

C/o? : ca>, 3

• hi in 4JN

(0 o a e

•B

iH CO | - a tn o -H (0 a ε 3

• en rH <u -H

.ro -h i e 3

: C0 3 03 (O

4-1 I (0 E a \ iDiD'O'UOOCNun ro

^ C3I3ECJ Oi C- O Οι Γ ~ O CO O

(CO 1-1 ί S i® ° «-4 en C-1-1 \ • H (0

CO '' 'O

No? rac0 o m O ro un O lti O uo ^ * H ^ fH 'Ή O 4J · Η

· Θ4-> CO

CO Q-

- CO

«= CO _A yy __ / u_ -H

• H 4-) - - - “r 4_> 3 (0 4-> CO 3 -Hl (0« «£ S -3 Λ (0 O (0 (0 3 (4 I -H>, 3 -H Q .3 I · Η m rt-1 Ή CT -H * H 3 oj>, fn C T3 -HM I 4-1>, Ί- '^ ra -H (0 C>. 3 3>, 03>,> , C 3 I 03>, CC0 3

EO >> C · —I 03 4-> -H (0 D

• H H> 03>,: 3 03 3 3 3 3 —H -H ChQ3 E> E (H Ch 03 3

y vm -C 3 I 4-1 O 03 03 CO O

> -> - «5 03 03 03 C 3 CO CO

O>, a-H c_ -H H 0 3> x Ή I

J * 3-H: (0 Q C3 E 03 3 (4 D

^ 03H Q, -H 03033 3 3 ε >>: c0 - * '3 3>, >> 3 I DC Χ> d rtH3i -h (h rt4CN3 ^ rmuDr- ^ 03 (0 O 0 O CO 03 03 0 I - 0. E 3 UE.> - * ^ 81369

For comparison, the last row of the table shows that aromatic plasticizers such as dibutyl ;. fta-tile, cause low UV transmittance, which further decreases upon irradiation.

Since it was also known that the addition of an external plasticizer to the methyl methacrylate polymerate has the same effect as the use of acrylic esters involved in the preparation of the polymer, i. lowering the softening temperature, it was completely unexpected that a decrease in the softening temperature is associated with an improvement in UV transmittance over a long period of time. In particular, it was surprising that the effect of the addition of plasticizer is even greater than the effect of the addition of acrylate and that the addition increases the UV transmittance.

The methyl methacrylate polymer can be formed entirely from this monomer, as is recommended. However, in addition to methyl methacrylate, up to 10% by weight of other miscible comonomers, based on the polymer, may also be present in the formation of the polymer. These include other esters of methacrylic acid, especially esters of C 2 -C 8 alkanols, alkyl esters of acrylic acid having in particular 1 to Θ carbon atoms in the alkyl group, and optionally crosslinking comonomers such as ethylene glycol dimethacrylate and the like. Less suitable are comonomers which absorb in the UV range, in particular monomers containing aromatic groups. These include, for example, styrene, vinyl toluene and benzyl acrylate and methacrylate.

When making new plastics, it is advantageous that the unpleasant-smelling acrylic ester can be omitted.

The molecular weight of the methyl methacrylate polymer may be in the conventional range for a plastic based thereon. At best, it is over 500,000, especially in an area of about 1-2 million. Plastics with such a high molecular weight are not extrudable or injectable and are therefore polymerized immediately as sheets or tubes. The polymerization is generally carried out in a flat chamber formed by two parallel glass sheets spaced 2 to 20 mm apart and a sealing strip running around the edge. The plastic is then obtained in the form of sheets 2 to about 18 mm thick, which in the thermally elastically softened state can be bent, stretched or reshaped into dome-shaped or trough-shaped.

The Vicat softening temperature (DIN 53 460) of pure polymethyl methacrylate is 118 ° C. By using comonomers together and adding a plasticizer according to the invention, the Vicat softening temperature decreases and is between 70 and 110 ° C, preferably between 95 and 105 ° C. The content of the residual monomer should be as low as 0.5 μm, preferably less than 0.2%, based on the weight of the plastic.

The sterically hindered amines contained in the new plastic are the same as those used in plastics according to EP-B 16 870. They have a general formula

R

--h * A N - R '

T - R

wherein R represents the same or different alkyl groups, R 'is a hydrogen atom or an alkyl group and A is an optionally substituted 2- or 3-membered alkylene chain. The groups R are generally lower alkyl groups having up to 4 carbon atoms, preferably methyl groups. R 'is preferably a hydrogen atom or a lower alkyl group, especially a methyl group.

However, R 'may also be a larger aliphatic group joined by the nitrogen atoms of the two amine groups of the above formula. This aliphatic group may have, for example, one or more ester groups. A is preferably a 3-membered 6 81 369 (alkylene chain in which the nitrogen atom belongs to a piperidyl group, in particular a 2,2,6,6-tetramethylpiperidyl group. The middle carbon atom of the 3-membered alkylene chain generally has a substituent which may optionally be bifunctional or multi-functional). and which may be attached to one or more groups of the formula

R

1-H

B N_ R »

1 - R

1 wherein B represents an alkylene group denoted by the symbol A above, however, one carbon atom contains a free valence. When a sterically hindered amine containing a group-unsubstituted, radically polymerizable group, for example an acryloxy, methacryloxy, acrylamido or methacrylamido group, is used in the manufacture of the plastic, the tertiary amine is attached to the methyl methacrylate polymer during polymerization.

Thus, a blend polymer is formed containing side groups of the last given formula.

Typical representatives of sterically hindered amines are: 7 81 369 CH> CH> 3l H c // i „po-co- (cy, -a, -CHi I CHi CHIh> h%, <** ^ fy-O-CO- (CHx), - C0 -O- c * rr CHj «>] - (oQ-CtW, -O-CO -CiHh -co-o-C2H ^ tTy-O-CO-CzHrCOj" - '/ \ CH n CH3 CH) 3 • i-1 ~ (ch ^ - ~ t — o ^ cc "'4 ^>«, £ u ^ h CKyti ~ y —- 0-C ° -c- CO — 0- / κι - 6H3 ch ^ \ u / Ϋζ cftj C «3 CH? ΡΗ \ Z \ ^ -0-C <CH3 hOc i ch> / s ^^ CO - NH CW) CH3 8 81369

The polymerized units of the compounds of the formula CH-I CH3 f CH0 = c-CO - XX NR 'SCc'3 CH3 where R = H or CH2, R' = H or CH2 and X = -O- or -NH- may be components of the polymer.

The permanently high transmittance of UV radiation, which further increases with the longer duration of the irradiation, is based on the fact that the plastic according to the invention contains an aliphatic peeling agent. Plasticizers are all aliphatic compounds which, when added from 1 to 10% by weight, reduce the Vicat softening temperature of the polymethyl methacrylate according to DIN 53 460 to 70 to 110 ° C, preferably to 95 to 105 ° C. This first requires that they be compatible with polymethyl methacrylate. Compatibility can be readily determined by dissolving 100 parts of polymethyl methacrylate and 1 to 10 parts of plasticizer in a volatile organic solvent such as chloroform and making a thin film from the solution.

When the film is completely clear after evaporation of the solvent, the plasticizer is compatible with the polymethyl methacrylate. If, on the other hand, it does not fit together, the film becomes cloudy during drying. Although in special cases it may be desirable to remove the plasticizer from the plastic again during or after further processing, it should generally remain in the plastic as a permanent ingredient. However, it has been found that this is not necessary for the beneficial effect of the addition of plasticizer. Rather, it is sufficient for the plasticizer to be present until the polymerization is completely stopped. High UV transmittance is also maintained when a volatile plasticizer is used and this 9 81 369 is subsequently removed from the plastic by sublimation in vacuo or by extraction as a solvent in which the plastic itself is insoluble. A plasticizer with a boiling point above 120 ° C does not usually escape from the plastic itself. A high-boiling softener with a boiling point well above 120 ° C is best used.

Many organic plasticizers conventional in plastics technology, namely plasticizers containing aromatic groups, are not suitable for the present invention. These include, in particular, phthalic acid esters. The plasticizers used according to the invention are aliphatic in nature. Their molecules consist of alkyl or alkylene groups and contain one or more ester, ether or hydroxy functions. Typical plasticizers of this quality contain 2-4 such functions. Examples of aliphatic softeners of the type used according to the invention are diethyl adipate, diethylene glycol monoethyl ether, glycerol triacetate or diethylene glycol.

The transmittance of UV radiation as well as its increase during irradiation increase with increasing concentration of plasticizer. However, since the Vicat softening temperature decreases to the same extent, a compromise must be reached between the desired UV transmittance on the one hand and the still sufficient Vicat softening temperature on the other hand. When the plastic is not exposed to high temperatures during its use, a significant decrease in the Vicat softening temperature can be tolerated; in this case, plasticizer additions of 5 to 10% by weight may be used. In contrast, when the Vicat softening temperature is allowed to decrease only slightly, a plasticizer addition of 1-3 weight-Si should not be exceeded. In most cases, the best addition rate is 3 to 5%, as a constant high UV transmittance and durability is already achieved in this range, but the softening temperature is not yet significantly reduced.

The new plastic is generally prepared by radical polymerization of a mixture containing 10 81369 A) at least 90% by weight of S ((based on the sum of the weights of components A and B) methyl methacrylate, B) 0-10% by weight (based on the sum of the weights of components A and B) copolymerizable a comonomer other than those belonging to the following group C, C) 0.01 to 1 by weight - based on the total weight of the mixture) of a sterically hindered amine of the formula given in claim 1, in addition to D) a conventional radical initiator or initiator system and E) 1 to 10 wt.% (Based on the total weight of the mixture) of an aliphatic plasticizer.

The mixture is raised in a manner known per se to a temperature at which the polymerization is triggered by a radical initiator or initiator system. All peroxide or azo type initiators known for radical polymerization are useful. Aliphatic initiators are preferred because aromatic initiators such as dibenzoyl peroxide form UV-absorbing degradation products. Examples of suitable aliphatic initiators are azo-bis-isobutyronitrile, dilauroyl peroxide, tert-butyl perpivalate, peroctoate or perneodecanoate or diisopropyl peroxydicarbonate. The polymerization temperature depends on the decomposition temperature of the initiator and is preferably between 30 and 80 ° C, in the final stage up to 120 ° C. The polymerization usually takes 15 to 20 hours. Aim for the most complete reaction possible; the residual monomer content should be as low as 0.5%, preferably less than 0.2 SS. It has already been mentioned above that the polymerization is best carried out in a flat chamber formed of two glass plates and a sealing strip. In this case, the 11,81369 prepolymerized monomer mixture can be filled into a flat chamber and polymerized within it. Plastic sheets made in this way are particularly suitable for the production of solarium bases. They can also be used to make glazing and similar coatings for UV radiators, greenhouses and swimming pools.

Example

The monomer mixtures given in Table 2 below were filled into flat chambers formed of two glass sheets and a 5 mm thick sealing strip around the edge between them. In addition to the ingredients mentioned in the table, these each contained 0.01% by weight of azo-bis-isobutyronitrile and 0.1% by weight of β-di (2,2,6,6-tetramethylpiperidyl) sebacate. Upon heating to the given temperatures, clear colorless polymer sheets formed through polymerization.

2)

Pre-Methyl- Softener approx. .. VET ^ Remo brand (weight) conditions * "" 13 "0 * ~ ~ ~ Ethyl adipate“ 2o h 40 «-4S ° +5 h 105 ° 96 2 90 10 Diethyl adipate 15 h 40 ° * +5 h 100 ° 76 0f16 3 97 3 Diethylene glycol- 15 h 40 ° monomethyl ether +6 h 100 ° 104 4 95 5 Diethylene glycol-- 20 h 40 ° -45 ° monomethyl ether +5 h 105 ° 95 5 90 10 Diethylene glycol- 20 h 40 ° -45 ° monomethyl ether +5 h 90 ° 70 o 15 6 95 5 Glycerin 20 h 40 ° -45 ° triacetate +5 h 105 ° 102 7 90 10 Glycerin 15 h 38 ° triacetate 5 h 90 ° 85 o 15 1) Vicat softening temperature, DIN 53 460 2) Residual monomer content by weight of the finished polymer

Claims (10)

12 81 369 A plastic consisting of a polymer formed of at least 90% by weight of methyl methacrylate and at most 10% by weight of comonomers copolymerizable with it and containing 0.01 to 1% by weight of a sterically hindered amine of the formula R, -hR A N-R 'IfR R wherein R represents the same or different alkyl groups, R' is a hydrogen atom or an aliphatic group and A is an optionally substituted 2- or 3-membered alkylene chain, the amine homogeneously distributed in the plastic or linked to the polymer via member A, characterized in that the plastic contains 1 to 10% by weight of an aliphatic, polymethyl methacrylate-compatible potato extractor boiling above 120 ° C. Plastic according to Claim 1, characterized in that the methyl methacrylate polymer has a molecular weight of more than 500,000. Plastic according to Claim 1 or 2, characterized in that the aliphatic plasticizer is a compound having one or more ester, ether or hydroxy functions. Plastic according to Claim 3, characterized in that the aliphatic plasticizer is a compound having 2 to 4 ester, ether or hydroxy functions. Plastic according to one of Claims 1 to 4, characterized in that the residual monomer content is less than 0.5% by weight. Plastic according to one of Claims 1 to 5, characterized in that the I / icat softening temperature is between 75 and 115 ° C. Plastic according to Claims 1 to 6, characterized in that it is in the form of sheets with a thickness of 2 to 18 mm. A process for preparing a plastic according to any one of claims 1 to 6 by polymerizing a mixture containing A) at least 90% by weight (based on the sum of the weights of components A and B) of methyl methacrylate, B) 0 to 10% by weight (based on the weight of components A and B) C) 0.01 to 1% by weight (based on the total weight of the mixture) of a sterically hindered amine of the formula given in claim 1, D) a conventional radical initiator or initiator system characterized in that 1 to 1% by weight of a comonomer is copolymerized with it, 10% by weight (based on the total weight) of an aliphatic plasticizer compatible with polymethyl methacrylate and boiling above 120 ° C. Process according to Claim 8, characterized in that the polymerization is carried out in a flat chamber formed by two parallel-moving glass plates spaced 2 to 20 mm apart and a sealing strip running around the edge. Plastic sheet according to Claim 7, characterized in that it is used as a solarium. ι »81369