HK1081572A - Polymer composition including a cyclic olefin copolymer - Google Patents

Description

Polymer composition comprising cyclic olefin copolymer

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The invention relates to a polymer composition comprising a cyclic olefin copolymer, to a film comprising a layer consisting of this composition and to specific applications thereof.

Medical articles must not only meet the usual requirements, such as good mechanical strength or low cost, but also the-very strict-requirements specific to this particular field of application, which relate, for example, to the biocompatibility of the article, its resistance to sterilisation, flexibility, transparency, weldability, impact strength (including containers for liquids), the amount of extractable material (for example with hexane) and, in some cases, barrier properties.

Until now, commercially available medical articles, such as infusion bags or blood bags, and bags for preserving medically relevant liquids, have been based on vinyl chloride polymers, such as PVC. Although these polymers have some advantages, they have some disadvantages, such as the need to incorporate large amounts of stabilizers to improve their thermal stability, or the need to incorporate large amounts of plasticizers to obtain sufficient flexibility. There is therefore a need in the market for medical articles that do not contain chlorinated polymers.

To obtain such articles, it is known to use films based on polyolefins as raw material, which are welded together (or themselves welded together) to make bags or pouches. Patent application WO00/61062 to SOLVAY describes such films which may comprise COP (cycloolefin polymers). However, this application found that when COP is used alone (i.e. as the sole component of the film or layer), welding is not easy and the resulting weld is of poor quality, especially in the case of short welding times which are commonly used in industrial processes. In addition to this, when pure COP is used, the heat sterilization effect, transparency and flexibility are not ideal even when used in only one layer of the multilayer structure. More particularly, multilayer structures comprising pure COP layers are susceptible to delamination after heat sterilization.

The applicant has surprisingly found that when adding syndiotactic polypropylene (s-PP) to COP, the former becomes easily weldable and can produce bags or pouches that can be heat sterilised, maintain (after sterilisation) clarity, flexibility, have high impact strength, exhibit excellent barrier properties (i.e. against water vapour, acids and alcohols) and do not delaminate after heat sterilisation when used in a multilayer structure. Furthermore, since s-PP is obtained by metallocene catalysts, the amount of extractable compounds is small and the residual catalyst is less than other non-metallocene PP resins.

Accordingly, the present invention relates to a polymer composition comprising COP and s-PP.

The term "COP" is to be understood as C₅～C₁₂Homo-or copolymers of cycloolefin monomers and/or bicyclic olefin monomers (dimers), which may be branched, to give a total of 5 to 30C. The copolymers generally comprise, in addition to the cyclic monomers, C₂～C₁₀The olefin content is 2 to 95 wt% (preferably 10 to 80%) and 5 to 98 wt% (preferably 20 to 90%) respectively. The basic cyclic monomer unit may be cyclopentene, cyclohexane, norbornene, dicyclopentadiene, tetracyclodecene or methyltetracyclodecene. Preferably norbornene:

bicyclo (2.2.1) hept-2-enes

If necessary with branching, it can be linear:

bicyclo (2.2.1) hept-2-enes

R1，R2(＝CxHy+1，x，y＝0，1，2，……)

Or cyclic, analogous to dicyclopentadiene (actually norbornene with cyclopentadiene branches):

the olefin is advantageously ethylene. COP is preferably a homo-or copolymer of norbornene, with or without branches; more preferred are homopolymers of norbornene (with or without branches, but preferably with cyclopentadiene branches, i.e.preferably dicyclopentadiene homopolymers) or copolymers of norbornene (with or without branches) with ethylene. In the latter case, the ethylene content is advantageously from 30 to 95% by weight (preferably from 40 to 80%) and the norbornene content is from 5 to 70% (preferably from 20 to 60%).

The s-PP according to the invention may be a homopolymer or propylene with up to 30% C₂～C₈Copolymers of comonomers, preferably ethylene. It is preferably a polyolefin with controlled crystallinity, as described in WO 00/61062. Preferably, the softening point (or "Vicat point") is lower than 121 ℃ (measured according to ASTM standard D1525), at least after processing under suitable conditions (described in WO00/061062, incorporated herein by reference), even if the producer of the resin alleges it to have a higher value. The s-PP according to the present invention therefore preferably shows a distinguishing feature, i.e. the crystallinity can be easily reduced during processing. In the context of the present invention, this preliminary control of the crystallinity is advantageous, given that suitable processing conditions are used, a reduced crystallinity of the s-PP resin is obtained, thus increasing the integrityTransparency and flexibility of the structure.

The polydispersity of the s-PP according to the invention is advantageously lower than 8 and preferably lower than 4. This feature reflects a low dispersion of molecular mass, which increases the separation between the range of melting temperatures and the range of softening temperatures and thus enables it to act more efficiently on crystallinity during processing.

Furthermore, the s-PP used advantageously has a melt flow index lower than 10g/10min, preferably lower than 6g/10min (measured according to ASTM standard D1238 at 190 ℃/2.16kg for ethylene polymers and butene copolymers and at 230 ℃/2.16kg for propylene polymers and butene homopolymers).

In the compositions according to the invention, the s-PP content is generally 1% or more, or even 10% or more (by weight relative to the total weight of the mixture), while the COP content of the mixture is generally 70% or more, or even 80% or more. Typically, the s-PP content is 30% or less, or even 20% or less, while the COP content is 99% or less, or even 90% or less.

In addition to s-PP and COP resins, the composition according to the invention may also comprise other thermoplastic polymers. The other polymers are advantageously chosen from polyolefins or hydrocarbons of the following types, of low crystallinity or amorphous:

-from at least two species C₂To C₁₀Olefin copolymers composed of olefins comprising at least 60% by weight of ethylene and/or propylene and/or butene, but comprising no more than 90% by weight of these comonomers, or

Comprising ethylene and/or propylene and/or butene and 10 to 40% by weight of one or more different comonomers, preferably C₅To C₁₀Olefins [ e.g. copolymers of ethylene and 1-octene, in amounts of Linear Low Density Polyethylene (LLDPE), Very Low Density Polyethylene (VLDPE) or Ultra Low Density Polyethylene (ULDPE)]And carboxylic acid or ester groups, e.g. vinyl acetate, methyl, ethyl or butyl acrylate and methylMethyl methacrylate, or carbon monoxide, or

Elastomeric copolymers having styrene and olefin blocks (e.g. styrene-butadiene-styrene copolymers, styrene-ethylene-butylene-styrene or styrene-ethylene-propylene-styrene type copolymers, and the like), or

Highly branched homopolymers [ e.g. Low Density Polyethylene (LDPE) or Medium Density Polyethylene (MDPE) ]

Hydrogenated hydrocarbons, e.g. paraffins or paraffin oils

Advantageously, the composition according to the invention also comprises at least one resin chosen from styrene-ethylene-butylene-styrene (SEBS), if necessary styrene-ethylene-butylene (SEB), styrene-ethylene-propylene-styrene (SEPS), if necessary styrene-ethylene-propylene (SEP), and ethylene-1-octene copolymers (preferably prepared with the metallocene process). SEBS and/or SEPS are preferred because they can be used to make permanently sealed and releasably sealed (at low temperatures) films and because they improve the impact strength of the composition. The total concentration of these resins is generally equal to or higher than 1% (by weight, relative to the total composition) and preferably equal to or higher than 10%. It is generally equal to or lower than 29%, preferably 20%.

The composition according to the present invention can be easily processed into various articles ranging from flat articles such as films or sheets to articles in three-dimensional spaces such as containers, and into articles of single-layer structure or multi-layer structure.

In a preferred embodiment, the present invention relates to a film comprising at least one base layer comprising the above composition.

The term "film" is used to indicate a thin, flat or tubular structure (in the case of blown film) having a thickness of typically 1000 μm or less, preferably 500 μm or less, or even 250 μm or less. In particular, a thickness of 100 μm or more, or even 150 μm or more is more suitable.

The film according to the invention generally has at least one further layer in addition to the base layer comprising the s-PP and COP composition. Since COPs are sensitive to greases, even in small amounts, for example on contact or handling, the film according to the invention preferably comprises at least one outer layer which does not contain COPs, and even preferably two such outer layers. In this case, the layers are located on both sides of the base layer. The additional layer preferably comprises at least 30% of PP (either syndiotactic or isotactic, or homo-or copolymer, for example copolymerized with ethylene) prepared by metallocene processes. The choice of the PP resin obtained by the metallocene catalyst process improves the purity of the whole structure (content of extractable residues and catalyst residues). For the same reasons as explained above, according to a preferred embodiment of the invention, the film comprises, on at least one side of the base layer, a layer comprising s-PP and/or i-PP prepared by metallocene process and at least one resin selected from the group consisting of SEBS, SEBS with SEB, SEPS with SEP and ethylene-1-octene copolymer prepared by metallocene process. The total concentration of these resins is generally equal to or lower than 70%.

In order to further improve the sealability of the film according to the invention, it is advantageous that the film comprises at least one outer layer (sealing layer) comprising s-PP and/or i-PP prepared by metallocene process; at least one resin selected from the group consisting of SEBS, SEBS and SEB, SEPS, SEPS and SEP, and ethylene-1-octene copolymers prepared by metallocene process; and at least one less crystalline or amorphous polyolefin selected from ethylene-vinyl acetate (EVA), ethylene-methyl acrylate (EMA), ethylene-ethyl acrylate (EEA) or ethylene-butyl acrylate (EBA) copolymers. Of the last-mentioned copolymers, only those having a comonomer content of at least 10% are considered as additional components. The concentration of these copolymers is generally equal to or higher than 0.1% (by weight, relative to the total composition), and preferably higher than 1%. It is generally equal to or lower than 15%, preferably lower than 10% and most preferably lower than 7%. Good results are obtained with a mixture of EVA and EMA, preferably in a total amount of at least 1%, or even at least 5%. It makes it possible to produce a weld with a high reproducible peel strength, which is useful for making articles with a peelable seal, such as multi-chamber bags or pouches comprising a permanent outer seal and at least one peelable seal.

In addition to the above-mentioned layers, it may also contain, from an economic point of view, a layer made of scrap (film of the invention) as an inner layer in the above-mentioned film.

To prevent blocking, the film according to the invention may be embossed (i.e. printed with a relief-like pattern) by any known process.

The film according to the invention may further comprise a barrier layer comprising a resin such as EVOH, PA or the like.

Preferred structures for the film according to the invention comprise the following layers:

1. layer A (outer layer) comprising at least 60% of s-PP and/or i-PP produced by metallocene technology and 0-40% of at least one resin selected from the group consisting of SEBS, SEBS and SEB, SEPS, SEPS and SEP and ethylene-1-octene copolymer produced by metallocene technology,

2. layer B (base layer) comprising an s-PP/COP mixture comprising at least 70% COP, at least 1% s-PP and from 0 to 29% of at least one resin chosen from SEBS, SEBS with SEB, SEPS, SEPS with SEP and ethylene-1-octene copolymers prepared by metallocene technology,

3. layer C (sealing layer) comprising at least 50% s-PP and/or i-PP prepared by metallocene process; 0 to 49% of at least one resin selected from the group consisting of SEBS, SEBS and SEB, SEPS, SEPS and SEP, and an ethylene-1-octene copolymer prepared by a metallocene process; and at least 1% of a mixture of EVA and EMA,

and a scrap layer located between layers a and B1.

Optionally, the preferred film may comprise an additional layer (B') between layers B and C, comprising at least 30% by weight of s-PP and/or i-PP produced by metallocene process and 0 to 70% of at least one resin selected from the group consisting of SEBS, SEBS and SEB, SEPS, SEPS and SEP and ethylene-1-octene copolymers produced by metallocene process.

The film according to the invention is easily welded and can therefore be used conveniently for the manufacture of bags. Accordingly, the invention also relates to a bag made from the above film. Preferably, the bag is a multi-chamber bag comprising at least one permanent outer seal and at least one peelable seal. Permanent seals are seals which are not easily peelable by hand and which usually have a peel strength of at least 2000N/m (according to ASTM/ISO F88), or even at least 3000N/m, whereas peelable seals are seals which are easily peelable by hand and which usually have a peel strength of less than 2000N/m. The optimum temperature, pressure and weld time ranges for a particular structure to achieve its permanent and peelable seals, respectively, can be readily determined by one of ordinary skill in the art with minimal experimentation. Typically, hot gas or hot tool welding is used to make permanent and peelable seals, with hot tool welding being preferred.

The films and bags according to the invention can be used in any field where flexibility, sealability, clarity, sterilization ability and barrier properties are suitable. The medical field is one such application. The bag according to the invention is indeed particularly suitable for containing medical liquids such as dialysis solutions, infusions, nutritional solutions and the like. Because of their excellent barrier properties to alcohols and acids, films according to the present invention can be welded into bags that store acids and alcohols, such as are used for rinsing or cleaning some medical devices. Very good results were obtained with the use of two-compartment bags, one containing a concentrated solution of acetic acid (up to 50% by weight) and the other containing water. The two chambers are separated by a peelable seal which is torn only before use to obtain an acetic acid solution of appropriate concentration. The bags according to the invention have a longer shelf life, i.e. produce less evaporation, than those according to the prior art.

Finally, the polymer compositions according to the invention can also be advantageously used for injection-molded articles. In most fields of application of the above-mentioned films and bags, the latter must be connected to some equipment (for example perfusion or dialysis equipment), and in order to achieve this connection, tubes or similar connecting means are generally used, these being generally prepared by injection moulding. In order to obtain a complete system with the same polymer composition and to obtain the advantages described above, the injection-moulded article advantageously contains the same polymer composition as described above.

Examples

In the following examples:

i-PP is EOD 9421 grade from ATOFINA (MFI 5 according to ASTM D1238)

SEBS is KRATON * G1657 grade from SHELL

EVA and EMA are UL00218 and 16 MA03 grades from ATOFINA (MFI about 3 and about 18% VA or MA)

COP is TOPAS * 8007 from TICONA (MFI (ISO 1133, 260 ℃, 2.16kg) 30)

Haze and clarity (total light transmittance) measured according to ASTM D1003-00

Films were prepared by coextrusion using a flat die and a feed head, each layer having its own individual single-screw extruder (diameter 60 and 45mm and barrel length 25D). The temperature of the mold, the feed head and the pipe joint is set to be about 220 ℃. The temperature from the inlet to the outlet of the cylinder is set to be 160-210/220 ℃.

-making a bag by welding the film through a hot tool under the following conditions: the temperature was 142 ℃, the pressure 6bar, and the time 1, 3 seconds.

Comparative example 1:

a multilayer film having peelable seal characteristics comprising:

layer a (outer layer): mixture of i-PP (90 wt.%) and SEBS (10 wt.%).

Layer B1: i-PP (100 wt%)

Layer B2: a mixture of i-PP (75 wt%) and SEBS (25 wt%).

Layer C (sealing layer): mixture consisting of i-PP copolymer (75 wt%), SEBS (22 wt%), EVA (2 wt%) and EMA (1 wt%).

The total thickness of the film was 200 μm and the layer B1 was 40 μm. Haze 4% and transparency 96%.

Comparative example 2:

the same as in comparative example 1 except that the B1 layer consisted of COP (100 wt%). The total thickness of the film was 200 μm and the layer B1 was 40 μm. Haze was 5% and transparency was 95.5%.

Example 3: films according to the invention

The same as in comparative example 1, except that the B1 layer consisted of a mixture of COP (85 wt%) and s-PP (15 wt%).

The total thickness of the film was 200 μm and the layer B1 was 40 μm. Haze 6.2% and transparency 95%.

Steam sterilization and drop test:

10 bags were made with the films of comparative example 2 and example 3, respectively, and 3 liters of water were charged; 5 of each group were steam sterilized (121 ℃/250 ° F, 30 minutes). After steam sterilization, the bags made from the films of comparative example 2 showed delamination. The bag according to the invention (example 3) showed no delamination. Both the sterilized and the non-sterilized samples were subjected to a drop test, which showed that the bags according to the invention survived the drop test from a height of 2 m onto a flat ground, whereas the bags made from comparative example 2 did not survive the test.

Storage of aqueous acetic acid:

bags made from the film according to comparative example 1 and bags made from the film according to example 3 were filled with 50ml of aqueous acetic acid at a percentage change (0, 24, 48, 74, 96%). The total surface area of all the bags was 150cm². The bags were stored at 23 ℃ and 40 ℃ for 135 days, and the results (average of two samples) are shown in Table 1.

Table 1: after 135 days of storageThe weight loss in grams of the water and acetic acid mixture at 23 ℃ and 40 ℃.

	23℃	23℃	40℃	40℃
					％HAc	Comparative example 1	Example 3	Comparative example 1	Example 3
0	-0,298	-0,244	-3,66	-2,851
					0	-0,302	-0,317	-3,772	-3,333
24	-0,26	-0,208	-3,521	-2,49
					24	-0,281	-0,235	-3,521	-2,965
48	-0,263	-0,168	-4,136	-2,296
					48	-0,265	-0,198	-4,143	-2,54
74	-0,271	-0,098	-5,075	-1,614
					74	-0,289	-0,116	-5,292	-1,91
96	-0,402	0,114	-9,862	-0,188
					96	-0,46	0,146	-10,327	-0,171

% HAc is the weight percentage of acetic acid in solution

As can be seen from the results of table 1, the bags/films/compositions produced according to the invention show a rather low weight loss. Accordingly, less acetic acid is leached and thus less odor is produced.

Mechanical properties:

the film according to comparative example 2 had a stress at break of approximately 50%, whereas the film according to example 3 had a stress at break of 150%, and its modulus of elasticity (according to ASTM D-882/ISO 178/DIN 53457) was reduced by 70MPa when compared with the film according to comparative example 2. This means that the bags/films/compositions according to the invention are more flexible than those of the prior art.

Claims (10)

1. A polymer composition comprising a Cyclic Olefin Polymer (COP) and a syndiotactic polypropylene (s-PP).

2. The polymer composition according to claim 1, wherein the COP is a homo-or copolymer of norbornene with or without branching.

3. The polymer composition according to any of the preceding claims, further comprising at least one resin selected from the group consisting of SEBS, SEBS with SEB, SEPS with SEP and ethylene-1-octene copolymers prepared by metallocene process.

4. A film comprising at least one base layer comprising a polymer composition according to any preceding claim.

5. Film according to claim 4, comprising on at least one side of the base layer a layer comprising s-PP and/or i-PP (isotactic polypropylene) produced by metallocene process and at least one resin chosen from SEBS, SEBS with SEB, SEPS, SEPS with SEP and ethylene-1-octene copolymers produced by metallocene process.

6. A film according to claim 4 or 5, comprising at least one outer layer comprising s-PP and/or i-PP prepared by a metallocene process; at least one resin selected from the group consisting of SEBS, SEBS and SEB, SEPS, SEPS and SEP, and ethylene-1-octene copolymers prepared by metallocene process; and at least one resin selected from the group consisting of EVA and EMA.

7. A film according to any of claims 4 to 6, comprising the following layers:

1) layer A (outer layer) comprising at least 60% of s-PP and/or i-PP produced by metallocene technology and 0-40% of at least one resin selected from the group consisting of SEBS, SEBS and SEB, SEPS, SEPS and SEP and ethylene-1-octene copolymer produced by metallocene technology,

2) layer B (base layer) comprising an s-PP/COP mixture comprising at least 70% COP, at least 1% s-PP and from 0 to 29% of at least one resin chosen from SEBS, SEBS with SEB, SEPS, SEPS with SEP and ethylene-1-octene copolymers prepared by metallocene technology,

3) layer C (sealing layer) comprising at least 50% s-PP and/or i-PP prepared by metallocene process; 0 to 49% of at least one resin selected from the group consisting of SEBS, SEBS and SEB, SEPS, SEPS and SEP, and an ethylene-1-octene copolymer prepared by a metallocene process; and at least 1% of a mixture of EVA and EMA,

and a scrap layer located between layers a and B1.

8. Bags made by welding films according to any of claims 4 to 7.

9. The bag according to claim 8 which is a multi-chamber bag comprising at least one permanent outer seal and at least one peelable seal.

10. Injection molded article comprising a polymer composition according to any of claims 1 to 3.