JP2002293372A - External packaging of deoxidant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an external packaging of deoxidant which is excellent in oxygen barrier property, steam barrier property and pin-hole resistance, free from any environmental pollution in disposal by incineration, and suitable for storage and physical distribution. SOLUTION: In the external packaging of deoxidant which is formed of a film with oxygen barrier property and stores deoxidant therein, the film with oxygen barrier property is a multi-layered film comprising (A) a highly moisture-proof biaxially oriented polypropylene resin layer, (B) a biaxially oriented polyamide resin layer containing a crystalline nylon MXD6, and (C) a sealant resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen-absorbing agent package containing an oxygen-absorbing agent.

[0002]

2. Description of the Related Art In recent years, a method using an oxygen scavenger has been established as a simple and reliable method for preserving easily oxidizable articles such as foodstuffs, pharmaceuticals, cosmetics, and the like, which are susceptible to microbial contamination and spoilage such as mold. Oxygen absorbers in the form of pouches, sheets, films and the like have been industrially manufactured.
These oxygen absorbers can be obtained by collecting a certain number of pouch-shaped oxygen absorbers, or by cutting a sheet-shaped or film-shaped oxygen absorber into a certain length, or by continuous packaging of a pouch-shaped oxygen absorber. Each bobbin whose body (web) has been wound up by a certain number is packaged with an oxygen barrier film and stored and subjected to a distribution process.

Conventionally, a stretched nylon (KON) / polyethylene (PE) coated with polyvinylidene chloride (hereinafter, for example, laminated in the order of a KON layer and a PE layer) has been used as an oxygen barrier container for storing an oxygen scavenger. Multilayer films are referred to as KON / PE).

However, in recent years, as a large number of packages containing oxygen scavengers have been manufactured and the distribution process of product transportation has become complicated and intense, physical handling of the conventional KON / PE package has been increasing. Insufficient strength may cause pinholes in the multilayer film during the transportation and distribution process, and the oxygen invading the oxygen scavenger may cause a situation. In order to be able to be handled practically, sufficient pinhole resistance is required, and its piercing strength needs to be 12 N or more.

On the other hand, packaging materials having excellent gas barrier properties include saponified ethylene-vinyl acetate copolymer (EV).
OH) A resin layer and a layer composition including a polyamide resin layer made of a blend of crystalline nylon MXD6 and another nylon are disclosed in Japanese Patent Application Laid-Open No. Hei 4-216050, in which a heat seal layer / a biaxially stretched EVOH layer / polypropylene, nylon or The layer configuration of the polyester biaxially stretched film layer is disclosed in
Each is described in JP-A-3-35778. However, the saponified ethylene-vinyl acetate copolymer layer (EVOH), which is the base material of the intermediate layer, has a weak steam barrier property and is insufficient as a container for storing and distributing an oxygen scavenger.

[0006]

In an oxygen barrier film for packaging an oxygen scavenger, the oxygen scavenger sometimes contains water which is a catalyst for developing oxygen absorbing activity. High water vapor barrier properties so that it does not volatilize outside the container.Generally, because it is stored and stored under reduced pressure by degassing operation, it has high strength and pinhole resistance, and can withstand severe handling in the logistics process. Is required to have sufficient strength and pinhole resistance, and to have good operability at the time of sealing or opening.

[0007] Further, as for the chlorine-containing material, there is a concern that a chlorine-containing compound is generated at the time of incineration disposal to cause environmental pollution. Therefore, a chlorine-free material is desired. An object of the present invention is to solve the above-mentioned problems of the prior art in the storage and distribution of an oxygen scavenger, and to provide an oxygen barrier property, a steam barrier property and a pinhole resistance that are well-balanced and functionally satisfactory. An object of the present invention is to provide an oxygen-absorbing package using a material that does not cause environmental pollution at the time of disposal.

[0008]

As a result of studying a method for solving the above-mentioned problems, the present inventor has found that (A) a highly moisture-proof biaxially oriented polypropylene (highly moisture-proof OPP) layer, (B) a stretched polyamide resin layer, (C) A multilayer stretched film including a sealant resin layer, wherein the polyamide resin (B) is crystalline nylon MXD6 alone or crystalline nylon MXD6
Of nylon with other nylon or crystalline MX
A stretched laminated film composed of a composite film of D6 nylon as a base material and another resin film (a film containing the crystalline nylon MXD6 in the above sense is referred to as a crystalline nylon MXD6-based film in the present invention) is used. As a result, it has been found that the object can be easily achieved, and the present invention has been completed.

That is, the present invention relates to an outer package of an oxygen absorber comprising an oxygen barrier film containing an oxygen absorber, wherein the oxygen barrier film comprises (A) a highly moisture-proof biaxially oriented polypropylene. An oxygen-absorbing agent outer packaging body comprising a multilayer film comprising a resin layer, (B) a biaxially stretched polyamide resin layer containing crystalline nylon MXD6, and (C) a sealant resin layer. With this configuration, the excellent oxygen barrier property of MXD6 is maintained, the steam barrier property and the pinhole resistance are improved to practical levels, and there is no need to worry about environmental pollution at the time of incineration disposal, and the oxygen absorber can be safely used. Is provided, which can be used for storage and distribution processes.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, (A) a highly moisture-proof biaxially stretched polypropylene resin layer, (B) a stretched polyamide resin layer containing crystalline nylon MXD6, and (C)
A multilayer film composed of a sealant resin layer is used.

The (A) high moisture-proof biaxially stretched polypropylene resin layer (high moisture-proof OPP) used in the present invention has a water vapor barrier property of 3.5 g / m ² · 24 hr or less at a layer thickness of 25 μm. It is a biaxially oriented polypropylene with high moisture resistance (synonymous with high steam barrier property). That is, since the water vapor barrier property of ordinary biaxially oriented polypropylene is about 7 g / m ² · 24 hr under the same conditions, a biaxially oriented polypropylene having a water vapor barrier property twice or more that of ordinary biaxially oriented polypropylene. It is.

The biaxially stretched polypropylene resin layer having high moisture resistance is formed by biaxially stretching a film made of a polypropylene resin composition obtained by adding a cyclic polyolefin, a petroleum resin, a cyclic olefin resin or a combination thereof to a crystalline polypropylene resin. This is a layer made of Specifically, 3 to 9 parts by weight of the petroleum resin, 91 to 97 parts by weight of the crystalline polypropylene, and 5 parts by weight of the cyclic olefin resin 5 with respect to the total weight of the petroleum resin and the crystalline polypropylene.
A polypropylene-based biaxially stretched laminated film in which a biaxially stretched layer of crystalline polypropylene is laminated on at least one surface of a biaxially stretched layer of a resin composition comprising 〜20% by weight.

Here, examples of the petroleum resin include a resin obtained by hydrogenating an alicyclic polymer obtained by (co) polymerizing cyclopentene or a derivative thereof or cyclohexene or a derivative thereof. Examples of the cyclic olefin resin include an ethylene / cyclic olefin random copolymer obtained by copolymerizing ethylene and a cyclic olefin, a ring-opened (co) polymer of a cyclic olefin, or a resin obtained by hydrogenating the same. And a) a graft-modified polymer.

The polypropylene resin composition constituting the highly moisture-proof biaxially oriented polypropylene contains auxiliary components such as antioxidants, antiblocking agents, lubricants, antistatic agents, coloring agents, concealing agents and other additives which are usually used. May be used.

The highly moisture-proof OPP of the present invention is biaxially stretched. The stretching ratio is not particularly limited as long as the stretching effect basically appears, but is usually 1.5 times or more in the warp direction, 2.0 or more in the weft direction, preferably 3.0 to 7.0 times in the warp direction. It is 5.0 to 12.0 times in the weft direction.

(B) Crystalline nylon MX used in the present invention
Biaxially stretched polyamide resin layer containing D6 (OMXD
6) refers to a crystalline nylon MXD6 single layer obtained by polycondensation of meta-xylylenediamine and adipic acid, or a stretched film composed of an MXD6-based polyamide resin layer composed of a mixture of crystalline nylon MXD6 and amorphous nylon It is a layer. A composite nylon film layer composed of crystalline MXD6 nylon and another nylon resin film can also be used. Crystalline nylon MXD6 is
It is produced by condensation polymerization of meta-xylene diamine (MXDA) obtained by ammoxidation and reduction of meta-xylene with adipic acid.

Further, other amorphous nylons mixed with crystalline nylon MXD6 may be prepared by a combination of dicarboxylic acid and diamine as raw materials, or by melt polymerization under pressure or decarboxylation using lactam, diisocyanate or the like. Can be used. Here, examples of the dicarboxylic acid include adipic acid, suberic acid, azelaic acid, terephthalic acid, and isophthalic acid. As the diamine, for example, hexamethylenediamine, trimethylhexamethylenediamine,
Isophoronediamine, bis-p- (aminocyclohexyl) methane, bis-p- (aminocyclohexyl) ethane and the like are used. As a lactam, for example, ε-
Caprolactam, lauroca prolactam and the like. As the diisocyanate, for example, diphenylmethane diisocyanate, tolylene diisocyanate and the like are used. Further, other nylon to be mixed can be obtained by a polycondensation reaction of ω-aminocarboxylic acid, a polycondensation reaction of dibasic acid and dicarboxylic acid, and the like. Nylon 6, nylon 12, nylon 11, nylon 6 -6, nylon 6-10, nylon 6-12, and copolymers or mixtures thereof.

(B) The weight ratio of crystalline nylon MXD6 to amorphous nylon constituting a single layer of crystalline nylon MXD6 or an MXD6-based polyamide resin layer comprising a mixture of crystalline nylon MXD6 and amorphous nylon is as follows: ,Ten
0/0 to 20/80. The MXD6-based polyamide resin consisting of crystalline nylon MXD6 alone or a mixture of crystalline nylon MXD6 and amorphous nylon has a stretching temperature of 50 to 1
Stretched at 50 ° C. under the condition of a draw ratio of 2 to 6 times and stretched MX
D6 nylon (OMXD6) is obtained. (B) The biaxially stretched polyamide resin containing the crystalline nylon MXD6 has a stretching condition at which a stretching effect is exhibited, for example, a stretching temperature of 50.
Biaxially stretched at a stretching ratio of 2 to 6 times at ~ 150 ° C,
Stretched polyamides are preferred.

The sealant resin layer (C) used in the present invention comprises low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and medium-density polyethylene (MDP).
E), polyethylene (PE) such as high-density polyethylene (HDPE), olefin resins such as polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMM)
A), ethylene-ethyl acrylate copolymer (EE
A), ethylene-methyl acrylate copolymer (EM
A), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMMA), ionomer (ION), etc. Ethylene copolymer resin. Among them, LD
Olefin-based resins such as PE and LLDPE are more preferably used.

Each of the layers (A), (B) and (C) can be laminated by an extrusion lamination method in which an adhesive resin (Ad) is used and is extruded and laminated between the respective layers. The adhesive resin (Ad) used at that time includes low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and medium-density polyethylene (MDP).
E), polyethylene (PE) such as high-density polyethylene (HDPE), olefin resins such as polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMM)
A), ethylene-ethyl acrylate copolymer (EE
A), ethylene-methyl acrylate copolymer (EM
A), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMMA), ionomer (ION), etc. In addition to the ethylene copolymer-based resins, modified polyolefin-based resins, for example, ethylene-vinyl acetate copolymer or ethylene-based elastomer, monobasic unsaturated fatty acid such as acrylic acid or methacrylic acid, or maleic Examples thereof include those in which an anhydride of a dibasic fatty acid such as an acid, fumaric acid or itaconic acid is chemically bound.

The package of the present invention is a layered material having a thickness of 250 μm or less. (A) The thickness of the highly moisture-proof biaxially stretched polypropylene resin layer is preferably in the range of 10 to 30 μm.
When the thickness is 10 μm or less, the pinhole resistance decreases, and when the thickness is 30 μm or more, the total thickness of the laminated film increases, and the handleability decreases. (B) The range of 15 to 30 μm of the biaxially stretched polyamide resin layer containing the crystalline nylon MXD6 is preferably functional and cost-effective. (C) The thickness of the sealant is
The range of 20 to 60 μm is preferred. For 20 μm or less,
There is a concern that the seal strength will be reduced and breakage during use will occur. 60
If the thickness is more than μm, the cost is increased, and the total thickness of the film is increased, so that the handleability is reduced. When an adhesive resin layer (Ad) for bonding these layers is used, the thickness thereof is preferably in the range of 10 to 25 μm in terms of workability, economy, and handling.

As a method for producing the outer package of the present invention, for example, in the case of a three-layer five-layer film of (A) / (Ad) / (B) / (Ad) / (C), first, (A) The adhesive resin layer (Ad) is melt-extruded between the highly moisture-proof OPP film and the (B) OMXD6 film while being rolled, and then laminated and adhered. Further, between the (B) OMXD6 film surface and the (C) sealant layer. The adhesive resin layer (Ad) is extruded, laminated and adhered to obtain the above-mentioned three types and five layers of the multilayer package.

Here, the film composed of the number of base film types (n) and the number of adhesive resin layers (m) is referred to as an n-type m-layer film. The adhesive resin layer has a thickness of 5 μm or more and 25
It is a layer of 0 μm or less. It does not include a layer having a thickness of less than 5 μm, such as a dry lamination adhesive or a coating agent. In the present invention, a material containing halogen such as vinylidene chloride is not used.

The multilayer film used in the present invention comprises (A) a high moisture-proof OPP and (B) OMXD
Each layer of the 6-system, (C) sealant is manufactured by individually manufacturing a film corresponding to each layer, and then bonding the layers with an adhesive resin or an adhesive. Examples of the bonding (lamination) method at that time include an extrusion lamination method in which the adhesive resin layer (Ad) is extruded and laminated between the layers, and a dry lamination method in which an adhesive is applied to each layer or a part thereof, pressed, and dried. can give. Specifically, the laminating method between the A / B layers includes (A) biaxially stretched polypropylene (highly moisture-proof OPP)
Resin layer and (B) stretched MXD6-based nylon (OMXD6)
Extrusion lamination method in which an adhesive resin layer (Ad) that has a thickness between layers and also serves as a cushion and also has a role of improving adhesiveness, because the direct adhesiveness with the resin layer is not good and the flexibility is somewhat lacking. Is more preferable than the dry lamination method in which the adhesive is thinly applied (generally, several μm or less) and attached. In addition, the extrusion lamination method and the dry lamination method can be applied between the B / C layers, but the extrusion lamination method is more preferable because the package needs some flexibility.

The outer package obtained by the present invention has a water vapor permeability of 0.6 g / m ² · 2 at 25 ° C. and 0 → 75% RH.
Less than 4hr, oxygen permeability is 20m at 25 ° C and 60% RH
1 / m ² · 24 hr · atm or less, and the piercing strength is 12 N / pen tip radius 0.5 mm and 50 mm / min or more. As a result of the study by the present inventors, it has been found that pinhole occurrence accidents are sharply reduced at a puncture strength of 10 N. So, in anticipation of the safety factor,
When the piercing strength is 12 N or more, it can be determined that the pinhole has practically good pinhole resistance in handling.

The oxygen absorber to be packaged is an oxygen-absorbing substance exemplified by iron and ascorbic acid, which is packaged in a breathable packaging material or mixed with a thermoplastic resin. It is an oxygen absorber in any form such as a shape and a film. Specifically, it is an accumulation of a pouch-shaped oxygen absorber, a bobbin wound around a continuous bag (web) of the pouch-shaped oxygen absorber, or a bundle or roll of the oxygen absorber in the form of a sheet or a film. .

The outer package of the present invention is a package for storing and distributing the produced oxygen absorber, but can be widely used as a package for other food and drink bottles and barrels. The outer package is usually sealed with the sealant layers and sealed by various heat-sealing methods, for example, a method such as a heat bar seal, an impulse seal, and a high-frequency seal, to obtain a bag-shaped container. Then, a certain amount of the produced oxygen scavenger is stored therein, and if necessary, a vacuum operation or a degassing operation is performed, and then the container is sealed and subjected to a storage and distribution process.

[0028]

The present invention will be described below in detail with reference to examples. The physical properties of the multilayer film or the oxygen-absorbing agent exterior package obtained in the examples were measured by the following methods. (1) Water vapor permeability Unit: g / m ² · 24 hr The obtained multilayer film was measured according to JIS-Z-0208. Oxygen permeability Unit: ml / m ² · 24 hr The obtained multilayer film is subjected to an oxygen permeability measurement apparatus (OXY-TRAN, manufactured by Modern Control Co., Ltd.) at 25 ° C. and 60% RH
100 type).

(3) Puncture strength (pinhole resistance)
Unit: N (Newton) / Pin tip radius 0.5 mm, 50
mm / min The obtained multilayer film is 1 mm in diameter and has a radius of curvature of 0.1 mm.
A 5 mm pin was pierced under a speed condition of 50 mm / min, and the load (N) when the hole was opened was measured. (4) Drop test A roll body formed by spirally winding a continuous bag (web) consisting of 3,000 small bag-shaped oxygen absorber packages (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: Ageless Z-23PTR) in series on a bobbin Was sealed by a heat sealing method while performing a depressurizing operation using the obtained multilayer film to obtain 10 samples of the oxygen-absorbing exterior package, and these oxygen-absorbing exterior packages were placed on a concrete floor from a height of 2 m. After the natural film was repeatedly dropped 10 times, the multilayer film was observed for damage or pinholes.

Example 1 Highly moisture-proof biaxially stretched polypropylene (highly moisture-proof OPP) having a thickness of 25 μm (trade name: WH-OP HM-, manufactured by Tosello Co., Ltd.)
1) While a film and a biaxially stretched crystalline nylon MXD6 (trade name: MX Nylon 6580, manufactured by Mitsubishi Gas Chemical Co., Ltd.) having a thickness of 15 μm on one side are fed by a hot roll so as to face each other, a low-density polyethylene-based film is interposed therebetween. Adhesive resin (Misolan 11P, manufactured by Mitsui Chemicals, Inc.)
It is melt extruded at 00 ° C., and is highly moisture-proof OPP / adhesive resin / MXD6 = 25/1 by the extrusion lamination method.
A 5/15 μm laminated film was obtained. Next, the MXD6 side of the obtained film and a linear low-density polyethylene (LLDPE) (trade name: TUX-FCD) film as a sealant resin are opposed to each other by a hot roll while being sent while facing each other. The high-density polyethylene-based adhesive resin is melt-extruded and bonded by an extrusion lamination method, and finally a high moisture-proof OPP / adhesive resin / MX
D6 / adhesive resin / LLDPE = 25/15/15/1
5/30 μm three-layer, five-layer film (total thickness 100 μm)
I got The obtained multilayer film is obtained by the method described above.
The water vapor transmission rate, oxygen transmission rate, and piercing strength (pinhole resistance) were measured. The results are shown in Table 1. Each measurement is
The test was performed 10 times to indicate the range of numerical values.

From Table 1, it was found that the pinhole resistance can be greatly improved and improved to 12 N or more, which is a reference value capable of practically handling, while maintaining the steam barrier property and the oxygen barrier property. Next, the obtained three kinds 5
A drop test was performed using the layer film. After the drop test, there was no breakage or pinhole in the oxygen absorber package. Furthermore, the adhesive resin layer (Ad) between the (A) layer and the (B) layer improved the adhesiveness in a cushioning manner, and had high flexibility and handleability (handleability).

[0032]

[Table 1]

Comparative Example 1 In Example 1, high moisture-proof OPP / adhesive resin / MXD
In place of No. 6, a biaxially stretched nylon (KON) coated with polyvinylidene chloride (trade name N-81, manufactured by Toyobo Co., Ltd.)
2AE), except that they were adhered by an extrusion lamination method, and a multilayer film was prepared in exactly the same manner, and the water vapor permeability, oxygen permeability, and piercing strength (pinhole resistance) were measured. The results are shown in Table 1. Next, a drop test was performed using the obtained multilayer film. After the drop test, pinholes were observed in the multilayer film of two samples among the ten samples of the oxygen-absorbing agent outer package.

Example 2 In Example 1, (A) a high moisture-proof OPP resin layer and (B)
The MXD6-based resin layer and the urethane-based adhesive (manufactured by Takeda Pharmaceutical Co., Ltd., trade name: A515 / A12) are bonded together by dry lamination (adhesive thickness: about 3 μm),
(C) A multilayer film was prepared in exactly the same manner except that a linear low-density polyethylene (LLDPE) (trade name: TUX-FCD, manufactured by Tosello Co., Ltd.) having a thickness of 40 μm was used as a sealant resin layer, and a water vapor permeability, Oxygen permeability and piercing strength (pinhole resistance) were measured. Table 1 shows the results.
It was shown to.

From the results shown in Table 1, the method of dry lamination between the (A) highly moisture-proof OPP layer and the (B) MXD6 layer can be simultaneously performed while maintaining the steam barrier property and the oxygen barrier property, and at the same time, a practical resistance. It can be seen that the pinhole property can be improved and improved. Next, a drop test was performed using the obtained multilayer film. After the drop test, none of the oxygen-absorbing agent exterior packages showed any damage or pinholes.

[0036]

According to the present invention, the water vapor barrier property and the oxygen barrier property can be maintained, and at the same time, the piercing strength (pinhole resistance) can be improved and improved to a sufficiently practical level. Without the worry of contamination,
It is possible to realize an oxygen-absorbing agent outer package that can safely store the oxygen-absorbing agent and other articles in a storage and distribution process. Further, in the oxygen-absorbing agent outer package of the present invention, since a material containing halogen such as vinylidene chloride is not used, there is no concern about environmental pollution at the time of incineration disposal.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65D 65/40 BSQ B65D 65/40 BSSQE F-term (Reference) 3E067 AA13 AB96 AB99 AC03 BA17A BB14A BB25A BC04A CA05 CA06 CA30 EA06 FA04 FC01 GD01 3E086 AB01 BA04 BA15 BA33 BB02 BB05 BB85 BB87 CA29 CA40 4F100 AK01C AK03D AK03E AK06 AK07A AK46B AK63 BA03 BA04 BA05 BA07 BA15 EH232 EJ38A EJ38B GB15 J11BJDYJDJJDYJDYJDYJDJD11

Claims (5)

[Claims] 1. An outer package of an oxygen-absorbing agent comprising an oxygen-barrier film containing an oxygen-absorbing agent, wherein the oxygen-barrier film comprises: (A) a highly moisture-proof biaxially stretched polypropylene resin layer; (B) A multilayer package comprising a biaxially stretched polyamide resin layer containing crystalline nylon MXD6 and (C) a sealant resin layer. 2. The oxygen barrier film according to claim 1, wherein (A) a resin layer and (B) a resin layer, or (B) a resin layer and (C) a resin layer, laminated by (Ad) an adhesive polyolefin resin layer. The outer package according to claim 1, wherein the outer package is a laminated multilayer film. 3. The oxygen barrier film is a multilayer film in which (A) a resin layer and (B) a resin layer or (B) a resin layer and (C) a resin layer are laminated by a dry lamination method. The outer package according to claim 1. 4. The oxygen barrier film according to claim 1, wherein (A) the resin layer has a thickness of 10 to 30 μm, and (B) the resin layer has a thickness of 1 to 30 μm.
The outer package according to claim 1, wherein the resin package has a thickness of 5 to 30 m and the resin layer has a thickness of 20 to 60 m. 5. The oxygen barrier film having a water vapor transmission rate of 0.6 g / m ² · 24 hr (25 ° C., 0 → 75%
RH) and the oxygen permeability is 20 ml / m ² · 2
4 hr.atm (25 ° C., 60% RH) or less, and
The piercing strength is 12N / ballpoint pen tip radius 0.5mm,
The outer package according to claim 1, which is at least 50 mm / min.