Low thickness antifragmentation plates

Details Low thickness antifragmentation plates Low thickness antifragmentation plates

1997-08-25

2002-02-05

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Composite

Of polyamidoester

C428S213000, C428S520000

Reexamination Certificate

active

06344274

ABSTRACT:

The present invention relates to multilayer transparent, antireflex, coloured or opaline, laminates having smooth or embossed surfaces, optionally thermomouldable with external layers of acrylic polymers, obtained by coextrusion or by compression molding or by casting, the laminates have anti-fragmentation properties and/or improved mechanical properties for use in building or in signs, in lighting, and in the medical field, etc.
In particular the invention relates to polymethylmethacrylate laminates with low thickness, in the range of 1.5 up to lower less than of 10 mm in thickness, preferably 2-5 mm.
The technical problem arises when a blunt instrument crashes into the panel or into the manufactured article obtained from the laminate the impact results in the formation of several fragments which cause undesired situations or of danger for whom and/or what lies under these structures.
Therefore an object of the present invention relates to panels/manufactured articles exhibiting superior antifragmentation properties and/or improved mechanical properties with respect to the crash.
The Applicant has unexpectedly and surprisingly found that it is possible to produce antifragmentation laminates based on acrylic polymers employing one or more polymeric continuous films which have an elastic modulus lower than that by PMMA of at least 30%, and/or elongation at break higher than at least 40, preferably of at least 60G measured by the test according to ISO 527 for laminates or films, or similar standards, placed inside the panel.
If only one film is utilized it can be placed about approximately in the middle of the panel, preferably it is placed closer to the tensile stress part during the impact (opposite surface to the surface subject to crash). In practice the film is placed preferably at a distance between 10 and 40% of the total thickness of the laminate with respect to the surface opposite to the surface subject to impact. It is also possible to produce the plate with two film insertions placed near both PMMA faces. According to a preferred embodiment of the invention additional films can also be inserted in the tensile stress part at distances generally of about 1 mm from each other.
The film has a thickness generally from 70 &mgr;m up to 3 mm, preferably from 90 &mgr;m to 2 mm. In the case of the preferred panels of the invention (2-5 mm), the film has a thickness comprised from 70 &mgr;m to about 1.5 mm, preferably from 100 &mgr;m to 1 mm.
The preferred polymers are transparent polyalkylenterephthalates with the alkyl of from 2 to 5 carbon atoms, for instance polyethylenterephthalate (PET), polybutylenterephthalate (PBT); polyvinylbutyral (PVB), transparent elastomers having an acrylic basis, transparent thermoplastic elastomers having a styrenic basis such as styrene/butadiene block copolymers, MBS type transparent copolymers having a styrenic basis, grafted polymers having a vinylic basis, such as maleic anhydride.
Polymeric films carried out by polymerization with ultraviolet light which comprise the following essential components:
(a) selected from the following components:
(a1) alkyl(meth)acrylate monomers having general formula:
 wherein
R
0
′″ can be H, CH
3
R
01
can be an alkyl from 1 to 10 carbon atoms, linear or branched when possible, preferably a linear alkylic chain, preferably from 1 to 6 carbon atoms, or a cycloalkyl alkyl from 5 to 15 carbon atoms, optionally containing heteroatoms, for instance cyclopenthyl or cyclohexyl;
(a2) aliphatic urethane oligomers di (tri) (meth)acrylates obtainable by reaction of a polyisocyanate, preferably di-tri-isocyanate having the general formula:
R′—(NCO)
q
 wherein R′ is an aliphatic chain from 1 to 10 carbon atoms, preferably from 2 to 6, or an (alkyl)cycloaliphatic chain wherein the alkyl has the meaning described above and the cycloalkyl is a cyclic ring from 3 to 6 carbon atoms, preferably 5-6,
q being an integer from 2 to 6, preferably from 2 to 3, with
dialcohols of general formula:
HO—R″—OH
 wherein R″ has the same meaning as R′; said prepolymer NCO or OH terminated is reacted with (meth)acrylic acid to obtain unsaturated terminations;
(a1) and (a2) can be also in admixture with each other, the amount of (a2) ranging from 20 to 80% by weight with respect to (a1), preferably between 20-40% by weight;
(b) selected from one or more of the following components:
(b1) polyalkylglycols di-poly-(meth)acrylates having the general formula:
 wherein
R
0
is equal to H, CH
3
R′″ is equal to H, alkyl from 1 to 6 carbon atoms, preferably 1,
m is an integer from 2 to 12, preferably from 3 to 10;
(b2) alkyl di-poly-(meth)acrylates having the general formula:
 wherein
R
0
is equal to H, CH
3
,
n′ is an integer from 2 to 10, preferably from 4 to 6;
(b3) polyallylglycidylethers having the general formula:
 wherein
n″ is an integer from 1 to 8, preferably from 3 to 6,
m′ is an integer from 2 to 10, preferably from 2 to 6,
R
0′
is equal to H or an alkyl from 1 to 10 carbon atoms, preferably from 1 to 6;
the mixture of (a) and (b) is such as to have a viscosity from 50 to 3,000 cPoises, preferably from 100 to 1,000;
the component (b) can be omitted if in the formulation the component (a2) is present;
(c) hydroxy or carboxy alkyls alkyl(meth)acrylate from 2 to 6 carbon atoms, in amounts comprised between 0.5 and 5% by weight on the total, preferably 0.5-2, having the general formula:
 wherein
R
0
is H or CH
3
,
R
02
is an alkyl from 1 to 10 carbon atoms, preferably from 1 to 6;
the amount of component (b) in the composition being comprised between 5 and 20% by weight, preferably between 5 and 10% by weight;
the film being obtained by UV polymerization in the presence of photoinitiators in amounts comprised between 1 and 10% by weight, preferably between 3 and 6% by weight;
the amount of (a) being the complement to 100.
The components of type (a2) are commercially known for instance as EB®: such as EB 230, EB 264, EB 284, EB 244 produced by the company UCB.
The components of type (a1) are for instance methyl-, ethyl-, butyl-, isobutyl-, ethyl-hexyl acrylate, etc.
The compounds (b1) are also known commercially as: SARTOMER® 252, SARTOMER® 400, commercialized by Cray Valley, or tripropylenglycoldiacrylate (TPGDA); compounds (b2) are well known, hexandioldiacrylate (HDDA) can be mentioned; compounds (b3) are known in trade as SANTOLINK® XI 100 commercialized by Monsanto.
Compounds (c) which can be mentioned are hydroxyethyl- and hydroxypropyl-acrylates o-methacrylates; alpha-hydroxyethyl(meth)acrylate, carboxyethyl(meth)acrylate, for instance 2-carboxyethyl(meth)acrylate, are preferred.
These polymers can be used alone or in admixture with each other or with other polymers, for instance PMMA, MMA/-styrene in such ratios as to maintain the transparence and the elongation and modulus properties as defined above.
As polymerization photoinitiators of radical type, induced by ultraviolet light, one can those based on benzophenone such as ESACURE® KT 37 and UVECRYL® P115 by Lamberti, or such as IRGACURE® 500 by Ciba-Geigy. DAROCUR® 1173 and the other compounds disclosed in EP patent 374,516 can also be utilized; alkylic or aromatic peroxides and/or hydroperoxides, for instance benzene peroxide, ter-butylhydroperoxide, laurylperoxide, lauroylperoxide, cumylhydroperoxide, etc. can also be utilized. The amount of radicalic photoinitiators as said above ranges from 0.5 to 5% by weight, preferably from 0.5 to 2% by weight.
Panels having an acrylic basis containing antifragmentation polymers can be obtained by compression moulding, by casting, by coextrusion or by sizing.
The industrially preferred process for preparing the antifragmentation panels of the present invention is coextrusion utilizing a feed-block or optionally a head having separated channels. The usual procedures to eliminate and/or reduce the possible encapsulation and unstability phenomena at the interface among the various polymer layers are obviously to be carried

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