JPS60101022A - Forming method of inflation film - Google Patents

Abstract

PURPOSE:To obtain an inflation film having an excellent thickness accuracy in a stable manner and in high efficiency, by using a polyolefin resin having a specific melt tension, and by fitting a die with a mandrel of specific structure for forming. CONSTITUTION:When a polyolefin resin having a melt tension of 3g or above is formed by an inflation method, the polyolefin resin is extruded to be tubular from a die 1 having an annular slit 2. The extruded tubular film 8 in the melted state is moved along a mandrel 3 formed of a netted body 4 which has a diameter being not smaller than the diameter of the annular slit 2 and not larger than 1.3 times thereof and virtually the same from top to the bottom and has 5-400meshes on the surface, and then it is taken out while inflated by air blown inside from an air intake port 5. It is desirable in terms of the stability of forming, the balanced strength of a produced film, etc. that the film be formed in the blow ratio of two or more approximately and by the factor of draft of four or more.

Description

[Detailed description of the invention] The present invention relates to a method for forming a blown film.

In detail, the present invention relates to a blown film forming method for forming a thin synthetic A04 resin film with good strength balance in a highly efficient and stable manner.

In recent years, packaging bags using synthetic resin films have become
4. From the viewpoint of the quality of interest rates, etc., the revision of fNr is being considered.

When forming the entire blown film, there is a method to avoid making the film thinner and to increase the draft rate.

However, inflation molding is a method of extruding resin into a cylindrical shape (all the air is blown into the interior of the resin to inflate it), so there are concerns about the inflated bubbles, especially when thinning the resin. Therefore, if molding is attempted by increasing the draft rate and/or blowing ratio, bubble oscillation and rupture tl:I'i occur, making stable molding very difficult.

In particular, when using synthetic 11J fat which has a high melting HQ tension, the cylindrical film extruded from the annular slit of the die causes so-called neck-in and is once thinned to a diameter smaller than the diameter of the monkey-shaped slit. 91 and then expands -j, so the part that supports the bubble becomes smaller in terms of actual TI, and there is a strong tendency for it to become unstable.

The inventors of the present invention have conducted extensive studies on a method for stably and rapidly molding thermoplastic synthetic resins with low melt tension, and have found that using a polyolefin resin with a specific melt tension, and molding a die with a specific structure. The present inventors have discovered that by attaching a mandrel and carrying out molding, a film that is extremely stable and has good thickness accuracy can be obtained with high efficiency, and the present invention has been completed.

That is, the gist of the present invention is that when performing inflation molding of a polyolefin resin having a melt tension of 32 or higher, the side facing the polyolefin is extruded into a cylindrical shape from a die having a thyropic slit, and the extruded cylindrical film in a bath-molten state is
Consisting of a net-like body having a diameter that is greater than or equal to the diameter of the annular slit and less than or equal to 1.3 times the diameter of the annular slit, the diameter is substantially the same from the bottom to the top, and the surface thereof shoulders the mesh of the 5-poo mesh. The present invention is a blown film forming method in which the film is moved along a mandrel and then taken off while being expanded.

An example of the method 1'/ξ of the present invention will be described below with reference to the drawings.

Fig. 1 tt'J, 4C'i6 Inflation film forming used in the method of Ming, l; % Ir'l -f11
It is an explanatory diagram without showing.

In the figure /f die, 2 is the current slit, 3Vi mandrel, dat'', net-like body, evening is the moss introduction hole, 6 and 7 are air outlet, glrJIMS-like film, 9 is air ring, t
All on-off valves are shown.

The polyolefin resin used in the method of the present invention -C includes polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-7゜ethylene 6j/dark vinyl copolymer, PJl-like low density polyethylene, etc. Among these, those having a la secondary tension of 32 or more are used.

Bath M: li tension wo', t+1IJie JIS K A
7 t, o o, t le) From the nozzle used in the index jll construction method /401:% /, 2.2
Extrude with m/rdm, /0. T is the tension measured at a distance from the nozzle when pulled at a speed of 2rn/mm.

Although it is possible to mold the film using ungrooved polyolefin (or fat) with a melt tension of 3F, it is difficult to obtain a film with satisfactory strength, especially tear strength and sanitary strength.

Among the above-mentioned polyolefin resins with a melt tension of 31 or more, the density is 0.93! High-density polyethylene with r t'1 crd or more and melt index / f / / θ min or less makes it easy to balance the vertical and horizontal orientation of the film.
Moreover, a film with high ultimate strength absorption can be obtained and can be suitably used in the molding method of the present invention.

Tie tI7) The cylindrical film extruded from the J'ss-shaped slit unit is attached to the mandrel 3 provided on the upper part.
It rises along the cylindrical body, is expanded by the air sealed inside the cylindrical body, and is taken away.

The diameter is substantially the same from the top to the top. The cylindrical film g extruded from the 9-shaped slit λ at the height of the mandrel 3 is at the so-called neck-in position tS.
That is, the can 1 in which the diameter of the cylindrical film S becomes smaller than the diameter of the slit tube due to natural shrinkage? 'I or more -, the helmet is indispensable, and the height is l, iX+! ,
Although there are particular restrictions on h',
It is preferable that the height is from the four-sided surface to the solidification point 1j (frost line) of the cylindrical film g.

Since the cylindrical film moves f2 along the mandrel 3 with such a diameter and height, the diameter of the cylindrical film g is 11'i-shaped slit λ even if the cylindrical film g is taken up at a continuous rate A. From the diameter of the river, the bubble is uneasy. It's fleeting.

Mandrel 3 surface tit American evening 1 la mark 11
The size of the mesh is 3~
qoo) mesh, fj-1 just t (/θ~λO
θ) Metshu, history VI-Good bite (Da O ~ 100)
It is formed from a reticulated body of the size of a mesh.

The mesh body has a thermal conductivity of 10 kcal/FIL in order to stabilize bubbles well when starting up the cylindrical film g.
It is best to use a material that exceeds -hr -C, and specifically, for example, a metal mesh made of stainless steel, aluminum, iron, or iron can be used.

Among these, stainless steel wire mesh is preferably used in terms of durability and corrosion resistance.

The mandrel 3 in the method of the present application may be any mandrel whose surface is formed of the above-mentioned net-like body, for example, a metal mandrel with the above-mentioned net-like body provided on the surface, or a metal mandrel with the above-mentioned net-like body formed on the surface of the mandrel. A mandrel with a single layer and the above-mentioned net-like body provided thereon, or a mandrel with the above-mentioned net-like body provided on the surface of a mandrel having a large number of through holes on the surface thereof, etc. are used.

By forming the above-mentioned network on the surface of the mandrel 30, not only the stabilization of bubbles when the cylindrical film g is started up is significantly improved, but also the adhesion of the molten cylindrical film l is prevented. There is also a young film 1t in which air J·11 is formed between the cylindrical film g and the mandrel 3 to reduce the pulling resistance.

Also, mandrel 3-key die l Kararoma! 11 hetL
411, the cylindrical film g extruded from the die l becomes thinner and expanded.
14 times, which may cause breakage, so the distance from the surface of the die to the position where substantially the same diameter portion of the mandrel 3 starts should be at least ///θ and less than l of the diameter of the wheel-shaped slit λ. It is desirable that

Performing inflation molding by the method of the present invention 1
It is preferable to mold with a blow ratio of 41 degrees, a blow ratio of 2 or more, a 17' rainbow, and a draft rate (take-up speed/extrusion speed) of i, i: + or more from the viewpoint of stability of molding, strength balance of the product film, etc.

Hereinafter, the method of the present invention will be further explained using actual Jfat examples, but the method is not translated into the following examples unless the scope thereof is exceeded.

Examples 1 to 3 High Density J, 11 Polyethylene (Sankyen Kasei Korai Steel ψ袈, Tsubachik Rda 0OOF, Melt Index (S: 0.019
710 minutes, density: θ, 9 left ef/di, melt tension crab qr
) (Tsubachik is a registered trademark of Mitsubishi Kasei Industries Co., Ltd.) f is used for an extruder of kOrtrmφ, an inflation molding device equipped with a die having a Jμ-shaped slit of !rOmmφ and a mandrel of left!bodyφ. temperature θ
Inflation molding was performed under the following conditions: OC, die head temperature λθθC, die temperature 20θC.

The mandrel is long! A stainless steel wire mesh with a mesh size of 0.000 trrm is provided on the side surface of an aluminum cylindrical body of 00 trrm.

The distance from the die surface to the position where substantially the same diameter portion of the mandrel begins was /Afrrrn. Bubble expansion is 3 from die! It started from the rOmn position.

The blow-up ratios J and II are constant, and the take-up speed is 1 m/min (Example 1), 30 m/min (Example 1), and 60 m.
/min (Example 3), and μ to 2, respectively.

A film with a thickness of -〇μ and 10μ was obtained and evaluated based on the bubble stabilization time, bubble stability, and strength balance of the obtained film.

The bubble L' stabilization time is expressed as the time (minutes) from when a tubular film in a molten state is melted onto the mandrel surface until it becomes possible to form a film in a stable state.

Evaluate bubble stability f′l by visually observing Shibapur!
Evaluation was made in three stages: L, , good, slightly unstable, and unstable.

Regarding the strength balance, tear the obtained film in the pulling direction with a metal bar, check whether the cut goes in the vertical direction, 4v1 direction, or diagonally.If the cut goes diagonally, it is considered to have good strength balance. All cases were classified as defective due to this.

The results are shown in Q/Clothing.

Examples D to S The mandrel of Example 1 was coated with a mesh size of 20 mm on its surface.
All inflation molding was carried out and evaluated in the same manner as in Example 1, except that the mesh (Example 1) or 8θ mesh (Example fl, left) was replaced with a mandrel equipped with a stainless steel wire mesh.

The results are shown in Part 1.

Comparative example / Implementation / Mandrel length! ; Depth θ, 7m+++, width 0 on the surface of an aluminum cylinder of 00tnyn
．． Inflation molding was performed and evaluated in the same manner as in Example, except that the mandrel was replaced with a mandrel in which mesh-like unevenness was provided by intersecting each other at a pitch of ek pitch/1 fryn at the five ends.

Results (f-shown in Table 1).

Comparative Example J, 3 Mandrel f3 of Example λ! In 11, all inflation molding was carried out and evaluated in the same manner as in Example 1, using the apparatus in which the mandrel of Example 1 was replaced (Comparative Example 3) and the mandrel of Example 1 was removed (Comparative Example 3). .

The results are shown in Table 1.

[Brief explanation of drawings]

FIG. 4 is an explanatory diagram showing an example of a blown film forming apparatus used in the method of the present invention. In the figure, 1-die, 2-piece thyroid slit, 3-piece mandrel, ``da'' is a net-like body, and ``da'' is a cylindrical film. and 7 others)

Claims (6)

[Claims] (1) Solu 1. f Q + J , i, H' above the diameter of the J-shaped slit
A diameter of 41 times less than 763 times that of the J-shaped slit.
++! From - to upper "11~, the cloud quality is the same diameter, and the moon has a mesh of S ~ qoo mesh f =
Place it on a mandrel made of N, move it 4 times, and then pull it out while tensioning it. 1. Inflated film forming method. (2) Polyolefin (November 1. Density 0,9.
7! The method according to claim 1, wherein the characteristics include polyethylene with a melt index of 78 or more and a melt index of 11,710 minutes or less. (3) Mantle v le FJ, h transmission exclusive lθkcal/+
The method according to claim 1 or 1, characterized in that it is made of gold copper, which has a good thermal conductivity exceeding ++ hr Ck. (4) The method according to any one of claims 1 to 3, characterized in that the surface of the mandrel L is made of a network having a mesh size of qO to 100 meshes. (5) Claims 1 to 5 characterized in that the distance from the die surface to the position where substantially the same diameter portion of the mandrel starts is greater than or equal to l/lO of the diameter of the annular slit. The method described in any of Section 7. (6) The method according to any one of claims 1 to 3, characterized in that the inflation molding is performed at a blow ratio of 2 or more and a draft rate of 2 or more.