Radiation-curing coating systems

Details Radiation-curing coating systems Radiation-curing coating systems

2001-10-19

2003-07-15

Seidleck, James J. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

C522S071000, C522S077000, C522S120000, C522S113000, C522S119000, C522S114000, C522S121000, C522S148000, C522S172000, C427S508000, C427S515000

Reexamination Certificate

active

06593393

ABSTRACT:

INTRODUCTION AND BACKGROUND
The present invention relates to radiation-curing coating systems, a process for their preparation and their use.
Radiation-curing coating systems are used to coat surfaces of wood, metals and plastics.
In some formulations the known radiation-curing coating systems have the disadvantage that the surface hardness is inadequate.
It is therefore an object of the present invention to develop radiation-curing coating systems which do not have these disadvantages.
SUMMARY OF THE INVENTION
The above and other objects of the present invention can be achieved by radiation-curing coating systems, which are characterized in that they comprise at least one silanized silica, where a silane from the group consisting of hexamethyldisilazane, 3-methacryloxypropyltrialkoxysilane and/or glycidyloxypropyltrialkoxysilane is used as the silanizing agent.
In a preferred embodiment of the invention, the silanized silica can be structurally modified. A silica such as described in the document EP 0 808 880 A2 can be used as the silanized silica. This document is incorporated herein by reference. The silica according to EP 0 808 880 A2 is a silanized silica with the following physico-chemical properties:
Specific surface area (BET)
m
2
/g
80-400
Primary particle size
nm
7-40
Tamped density
g/l
50-300
pH
3-10
Carbon content
%
0.1-15
DBP (dibutylphthalate) number
%
<200
This silanized silica is prepared by a process in which a silica is sprayed optionally first with water or dilute acid and then with a surface modification reagent or a mixture of several surface modification reagents in a suitable mixing vessel, with intensive mixing, the components are re-mixed for 15 to 30 minutes and heat-treated at a temperature of 100 to 400° C. over a period of 1 to 6 h, and the silanized silica is then destructured/compacted by mechanical effects and re-ground in a mill.
A silica prepared pyrogenically by the route of flame hydrolysis of SiCl
4
can preferably be employed as the silica. Hexamethyldisilazane, for example, can be employed as the surface modification reagent.
The coating according to the invention which can be cured by radiation comprises a reactive binder which contains double bonds in the terminal position or in the &bgr;-position relative to a reactive group which can be polymerized by free radicals. The double bonds can cure or polymerize under the influence of UV light or electrons. Copolymerizable reactive thinners (monomers) can be used to lower the viscosity.
Further components can be fillers, flatting agents and/or pigments. If required, wetting agents, flow control and degassing agents and other additives can be used in radiation-curing systems.
In UV technology, photoinitiators or photosensitizers are used to initiate the polymerization. In the case of curing by electron beams, the high-energy radiation itself forms the initiator radicals for the polymerization reaction.
The invention also provides a process for the preparation of the radiation-curing coating systems according to the invention, which is characterized in that 1 to 20%, preferably 2 to 10% of silanized pyrogenic silica, depending on the rheology of the system, is stirred into the coating system.
DETAILED DESCRIPTION OF INVENTION
The coating systems according to the invention can be used for coating a wide variety of surfaces such as derived timber boards, solid wood, wood veneers, parquet, decorative papers, decorative films, thermoplastics and thermosetting plastics, mineral and polymeric glasses, metals (for example aluminium, high-grade steel, phosphated, chromated and galvanized steel sheets, copper), lacquered surfaces, surfaces coated with printing inks and leather.
The radiation-curing coating systems according to the invention have the following advantages:
Improvement in the surface hardness, in particular scratch resistance, without impairment of the application properties, and in the optical properties of the crosslinked coating films.
According to the invention, the pyrogenically prepared silicas according to table 1 can be employed as the silica for the silanization.
Physico-chemical Data of Aerosil
AEROSIL
AEROSIL
AEROSIL
AEROSIL
AEROSIL
AEROSIL
AEROSIL
AEROSIL
Test method
90
130
150
200
300
380
OX50
TT600
Behaviour towards
hydrophilic
water
Appearance
loose white powder
BET surface area
1)
m
2
/g
90 ± 15
130 ± 25
150 ± 15
200 ± 25
300 ± 30
380 ± 30
50 ± 15
200 ± 50
Average primary
Nm
20
16
14
12
7
7
40
40
particle size
Tamped density
g/l
80
50
50
50
50
50
130
60
approx. values
2)
compacted goods
g/l
120
120
120
120
120
120
(added “V”)
VV goods
g/l
50/75
50/75
50/75
(added “VV”)
12)
g/l
120
120
Loss on drying
3)
%
<1.0
<1.5
<0.5
9)
<1.5
<1.5
<2.0
<1.5
<2.5
(2 hours at 105° C.) on
leaving supply works
Loss on ignition
4)7)
%
<1
<1
<1
<1
<2
<2.5
<1
<2.5
(2 hours at 1000° C.)
pH
5)
3.7-4.7
3.7-4.7
3.7-4.7
3.7-4.7
3.7-4.7
3.7-4.7
3.8-4.8
3.6-4.5
SiO
2
8)
%
>99.8
>99.8
>99.8
>99.8
>99.8
>99.8
>99.8
>99.8
Al
2
O
3
8)
%
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.08
<0.05
Fe
2
O
3
8)
%
<0.003
<0.003
<0.003
<0.003
<0.003
<0.003
<0.01
<0.003
TiO
2
8)
%
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
<0.03
HCl
8)10)
%
<0.025
<0.025
<0.025
<0.025
<0.025
<0.025
<0.025
<0.025
Sieve residue
8)
(Mocker
%
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.2
<0.05
method, 45 &mgr;m)
Drum size (net)
11)
Kg
10
10
10
10
10
10
10
10
1)
in accordance with DIN 66131
2)
in accordance with DIN ISO 787/XI, JIS K 5101/18 (not sieved)
3)
in accordance with DIN ISO 787/II, ASTM D 280. JIS K 5101/21
4)
in accordance with DIN 55921, ASTM D 1208, JIS K 5101/23
5)
in accordance with DIN ISO 787/IX, ASTM D 1208, JIS K 5101/24
6)
in accordance with DIN ISO 787/XVIII, JIS K 5101/20
7)
based on the substance dried for 2 hours at 105° C.
8)
based on the substance ignited for 2 hours at 1000° C.
9)
special packaging protecting against moisture
10)
HCI content is a constituent of the loss on ignition
11)
V goods are supplied in sacks of 20 kg
12)
VV goods are currently supplied only from the Rheinfelden works


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Copy of International Search Report for counterpart application No. EP 00 12 2956 dated May 4, 2001.
L.N. Lewis, D. Katsamberis: “uv-Curable, Abrasion-Resistant and Weatherable Coatings with Improved Adhesion”, J. Appl. Polym. Sci., Bd 42, Nr. 6, 1991, Seiten 1551-1556, XP002165547.

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