Aqueous compositions of perfluoropolyether phosphates and...

Details Aqueous compositions of perfluoropolyether phosphates and... Aqueous compositions of perfluoropolyether phosphates and...

2003-01-13

2004-09-14

Cheung, William (Department: 1713)

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

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S315000, C524S366000, C524S379000, C568S560000, C568S561000, C568S606000, C568S614000

Reexamination Certificate

active

06790890

ABSTRACT:

The present invention relates to aqueous compositions for the wet-end treatment of cellulose fibres/fibrilles for the manufacture of paper having oleo-repellence properties.
More specifically the invention relates to aqueous compositions based on fluorinated products capable to confer to paper an oleo-repellence capable to pass the application tests required by the manufacturers of oleo-repellent articles (grease-proof test) for the food or pet-food industry.
It is well known that the paper is used for the packaging of fats based on vegetable oils, of products as coffee, chocolate and also for the packaging of foods having a high fat content as meats, chips, hamburgers, popcorns, foods to be cooked in microwave ovens, and pet food. For said uses it is necessary that the paper be treated with products capable to confer resistance to oils and greases.
The oleo-repellence is commonly evaluated in terms of resistance of the paper sized to the penetration of the oil contained in hydrocarbon drops or hydrocarbon mixtures having a progressively decreasing surface tension, maintained for 15 seconds in contact with the paper specimen (Kit Test, TAPPI 557 method). Usually drops consisting of mixtures of castor oil, toluene and heptane in various ratios are used. The oleo-repellence values obtained with the Kit Test are however an index of the only surface activity of the fluorinated additive and often they have a poor correlation with the real performance in terms of protective barrier to oils and fats, both in normal utilization conditions of the paper packages in which there are prolonged contact times with foods, and in severe utilization conditions due to the temperature (heating of the food packages in microwave ovens) and mechanical stresses due to the bending to obtain the mnanufactured article. On this ground users utilize a series of tests considered more adherent to practical applications such for example:
Ralston Crease Test (RP-2 test): The resistance properties to the oil penetration in greaseproof papers for pet-food packaging are evaluated. The percentage of the surface of the paper stained by the coloured oil is determined. The specimen acceptability limit threshold is 2% of stained surface.
Resistance test to oleic acid: The resistance to oleic acid is evaluated at 60° C. for two hours. The test is passed when the paper is not stained and it does not show halos (% of stained surface=0).
Resistance test to fat acid mixtures: The resistance to a mixture of palmitic/lauric fat acids (C
16
/C
12
) is evaluated at 65° C. for 5 minutes. The test is passed when the paper is not stained and it does not show halos.
See the examples for the detailed description of said tests.
Compositions to confer oleo-repellent properties to the already formed paper are known in the prior art. However it is well known that the compositions used for said treatments are not necessarily effective when used for wet-end applications. In fact when said compositions are added to the paper slurry, to confer oleo-repellence they must be uniformly adsorbed on the paper fibrilles, which not always happens since said compositions can interact with the various additives present in the paper slurry, such for example polymer retention agents.
Known oleo-repellent compositions contain fluorinated components among which phosphates containing perfluoroalkyl groups, polymers containing pendent perfluoroalkanes with respect to the backbone and/or derivatives thereof in the presence of surfactants having a perfluoroalkyl chain (for example U.S. Pat. No. 5,271,806) can be mentioned. Said commercially used components contain perfluoroalkyl segments which by degradation give rise to perfluorooctyl components to be avoided since they tend to bioaccumulate. See for example patent WO 01/30873.
In U.S. Pat. No. 6,221,434 the use of (per)fluoropolyether phosphoric mono- or diesters for the paper surface sizing to confer oleo-repellence is described. According to the examples said components are used, also in salified form with NH
4
OH, in an aqueous solution containing isopropyl alcohol in a weight ratio 4:1 and 10:1 with respect to the component, in which the paper is dipped. In this patent no mention is made to the use of said components for their wet-end application of the paper. Tests carried out by the Applicant in the paper wet-end application using said compounds in aqueous solution containing isopropanol in a weight ratio with said compounds 4:1 have shown that said components are unable to confer satisfactory oleo-repellence values to pass the application tests required in the food industry (see the comparative Examples).
The need was therefore felt to have available aqueous compositions which in the wet-end applications conferred to paper an oleo-repellence capable to pass the most severe performance tests, such as those of resistance to oleic acid and to fat acid mixtures.
The Applicant has unexpectedly and surprisingly found specific aqueous compositions based on (per)fluoropolyether phosphates capable to satisfy the above mentioned requirements.
An object of the present invention are aqueous compositions comprising the following components:
I) a phosphate selected from the following
T—O—[R
f
—CFY—L—O]P(O)(O
−
Z
+
)(OH)  (A)
(OH)
m
(O
−
Z
+
)
2-m
P(O)[O—L—YFC—O—R
f
—CFY—L—O—P(O)(O
−
Z
+
)]
m′
—[O—L—YFC—O—R
f
—CFY—L—O]P(O)(O
−
Z
+
)
2-m
(OH)
m
  (B)
or mixtures of A) and B)
wherein
m′ is an integer from 0 to 20, preferably from 0 to 4;
L is an organic group selected from —CH
2
—(OCH
2
CH
2
)
n
—, —CO—NR′—(CH
2
)
q
—, with R′=H or C
1
-C
4
alkyl; n is a number from 0 to 8, preferably from 1 to 3; q is a number from 1 to 8, preferably from 1 to 3;
Z
+
=alkaline metal ion or a NR
4
group with R=H or C
1
-C
4
alkyl or an aliphatic amine ion;
Y=F, CF
3
;
m is a number between 0 and 1, extremes included;
R
f
is a (per)fluoropolyoxyalkylene chain having a number average molecular weight between 350 and 8,000, preferably between 500 and 3,000, formed by repeating units, statistically distributed along the chain, having at least one of the following structures:
(CFXO), (CF
2
CF
2
O), (CF
2
CF
2
CF
2
O), (CF
2
CF
2
CF
2
CF
2
O), (CR
4
R
5
CF
2
CF
2
O), (CF(CF
3
)CF
2
O), (CF
2
CF(CF
3
)O),
wherein
X=F, CF
3
;
R
4
and R
5
, equal to or different from each other, are selected from H, Cl, or perfluoroalkyl from 1 to 4 carbon atoms;
T is a (per)fluoroalkyl group selected from —CF
3
, —C
2
F
5
, —C
3
F
7
, —CF
2
Cl, —C
2
F
4
Cl, —C
3
F
6
Cl, optionally substituted with one or two H atoms, preferably one, at the place of F atoms; and
II) a solvent selected from C
1
-C
5
aliphatic alcohols, preferably isobutanol, aliphatic and cyclic ethers, preferably tetrahydrofuran, aliphatic acetates and mixtures thereof
wherein the ratio by weight between components I and II is in the range 1:1-1:0.05, preferably 1:0.5-1:0.1.
When component I) having formula (B) is used, mixtures of components B) wherein m′ is different from 0, preferably 1, can be used with components B) wherein m′=0, in a molar ratio in the range 5:95-50:50.
In particular R
f
in the (A) and (B) structures can have one of the following structures:
1) —(CF
2
O)
a′
—(CF
2
CF
2
O)
b′
—
with a′/b′ comprised between 0.5 and 2, extremes included, a′ and b′ being integers such to give the above mentioned molecular weight;
2) —(C
3
F
6
O)
r
—(C
2
F
4
O)
b
—(CFXO)
t
—
with r/b=0.5-2.0; (r+b)/t is in the range 10-30,
b, r and t being integers such to give the above mentioned molecular weight, X has the above indicated meaning;
3) —(C
3
F
6
O)
r′
—(CFXO)
t′
—
t′ can be 0;
when t′ is different from 0 then r′/t′=10-30,
r′ and t′ being integers such to give the above mentioned molecular weight; X has the above indicated meaning;
4) —(OCF
2
CF(CF
3
))
z
—OCF
2
(R′f)
y
—CF
2
O—(CF(CF
3
)CF
2
O

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