Odor reduction in laser processed material

Abstract

The present invention includes methods for treating a laser-processed material that produces an odor due to the laser processing. The present method includes treating the laser-processed material with heat to dissipate the odor from the material. The method can also include a cooling step after heating of the laser-processed material. Multiple cycles of heating and cooling may also be performed to substantially reduce or eliminate the odor from the laser processed material. The invention also includes an article made according to the method and apparatus for laser processing with the produced article having substantially reduced odor.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of U.S. provisional patent application Ser. No. 61/645,202, filed May 10, 2012, the content of which is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to laser processing of materials, and more particularly to reduction of odor caused by laser processing.

BACKGROUND

Lasers are well-known devices used in many areas of industry including production of packaging materials. Production of packaging materials has conventionally been performed by die based systems. Conventional die based systems require not only large areas to store the dies, but also time to set a die to run a particular package configuration. The use of lasers offers the ability to produce packaging based on a digital format. An almost endless library of digital patterns can be neatly stored and organized on computing devices. These patterns are readily available for loading into laser based systems and can be ready to begin new production jobs in a fraction of the time that was needed for a die based system.

Use of laser-based systems allows companies the potential to eliminate conventional die based converting, along with the costly manufacture, maintenance, storage, and changeover costs associated with dies. While dies may continue to be the tool of choice for a number of applications, they are not always the best choice. As the laser industry continues to advance and mature, more and more applications have and will become laser based.

One of the advances necessary for this continued growth lies in the area of reduced post processing odor. While lasers offer a number of advantages, one of the disadvantages can come in a lingering odor that may be present post processing or converting. The odor can be a burnt odor and is undesirable in a number of applications of the converted materials. A large number of the high speed laser processing systems are CO₂ based which operate in the mid infrared region and as such are heat based. The majority of the residue in laser-processed material is removed during processing in the form of vapor and particles. However, some can remain and cause an unacceptable odor. Porous materials can make this matter worse as odor causing compounds can be trapped in the porous areas. Paperboard is one such material that is well suited for converting with the CO₂ laser. Unfortunately, paperboard can have an unacceptable odor post laser processing. In some areas of industry this odor is minimal and is tolerable while in others it is unacceptable.

SUMMARY

This disclosure includes a method for reducing odors from a material, the odor having been caused by laser processing of the material. The method comprises heating the material to a temperature sufficient to substantially reduce the odor.

This disclosure also includes an article that was produced in part by utilizing a laser with the laser processing causing an odor and the odor having been substantially reduced or eliminated by heat treatment.

This disclosure also describes an apparatus for producing an article that has been processed by a laser with the laser processing causing an odor. The apparatus comprises a laser system that processes the material in part by burning and a heating system for heating the material during or after the burn to reduce or eliminate odor caused by the burning.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are a flow diagrams of a process for odor reduction in laser processed materials.

FIG. 2 is a schematic diagram of an apparatus for reducing odors in laser processed materials.

FIG. 3 is a schematic diagram of an apparatus for reducing odors in laser processed materials.

DETAILED DESCRIPTION

This disclosure relates to reduction of odor in materials that have been processed using a laser system. Methods of reducing odor from material that has been processed by a laser are disclosed. Such laser processing includes cutting and scoring. It has been found that the odor arising from the use of a laser system is reduced significantly by the application of heat to the material. Heat is applied using a variety of techniques. In some embodiments, one or more cycles of heating and cooling have been found to be advantageous for eliminating substantially most of the odor from the laser processed material.

This disclosure also includes articles made from material, particularly porous material processed by a laser that are substantially odor-free. The article can be used immediately after odor reduction without the presence of the offending odor which is generated during laser processing. The article is treated by heat to reduce or eliminate the odor.

This disclosure also describes apparatus that is used to reduce odor in and/or eliminate odor from material processed by a laser. The apparatus includes a heating system to heat the material for reducing or eliminating the odor. The laser treated material is heated immediately after being processed by the laser, although the material may be heated sometime afterwards. Immediate heating can result in better process efficiencies.

A cooling step after heating in some situations helps in further reducing or eliminating the odor by allowing the use of multiple heating cycles. The act of cooling in and of itself is not suspected to have any odor reduction affect. The apparatus may then also include a mechanism for cooling the material after it is heated for multiple heating cycles.

The apparatus may also include a laser system that processes the material with the laser and then immediately heats the processed material after it has been processed by the laser. The apparatus may then include a cooling system for cooling the material immediately after the material is heated. The laser system, the heating system and the cooling system can be in a variety of configurations as described herein.

A laser system or a laser-based system as referred to herein relates to a system that processes materials through the use of laser technology. Lasers are used in a variety of ways to produce packaging for products.

Many products are packaged in paperboard which is a thick paper-base material. It is derived from wood pulp and more recently from recycled waste paper (which also has its origin from wood pulp). It should be understood that paperboard may be called by other names, such as cardboard, kraft board, and the like.

Paperboard is generally thicker than paper (usually over 0.25 mm) and is typically in individual sheets or in a continuous sheet drawn from a roll. From the paperboard, packaging blanks are cut and portions of the blanks may also be scored so the blanks can be bent to form the walls of the package. Certain other portions can also be scored to form flaps that overlay each other and are then secured to each other by a suitable adhesive to form the package.

In recent years, lasers are being used more to cut and score packaging blanks. Lasers provide a very efficient method of cutting and scoring packaging blanks over the old mechanical die systems. Lasers cut and score through the use of a collimated amplified beam of light that terminates in a focal point. It is at the focal point of the beam that cutting and scoring takes place. Intense heat at the focal point cuts and scores the paper in what can be described as essentially a burning process. A by-product of burning a cellulose based material is the distinctive odor of burnt paper. In many packaging applications, this distinctive burnt paper odor is not troublesome. However, there are applications in which the odor is objectionable. One such application is cigarette packaging. Consumers often smell cigarette packages and expect a distinctive tobacco aroma. When the package is cut and scored by a laser, the burnt paper odor may taint the tobacco aroma (as well as the tobacco flavor itself) and be found objectionable. Such a burnt paper order would also be objectionable in other applications such as perfume boxes, scented soaps and the like.

Lasers have also been recently used to mark (etch) or cut leather products. (See U.S. published application 2011/0045237) Again, a distinctive odor is caused by burning leather with a laser. Leather is a product which has certain desirable olfactory characteristics. The odor of burnt leather would work against the desirable “leather smell” that most consumers are familiar with and desire. This disclosure also encompasses manmade materials that simulate leather.

Although cellulose based materials and leather are specifically mentioned herein, this disclosure encompasses other materials that can be processed by a laser and because of such processing a burnt odor is developed and may be found objectionable.

Another characteristic of materials that may produce an undesirable odor are materials that are generally porous materials. Such materials may also be “natural” materials. A “natural” material is any product derived from plants or animals. This disclosure also encompasses materials that are manmade such as polymeric sheets whether comprising a single polymeric layer or multiple layers of different polymers which are common in present day packaging. This disclosure also encompasses cellulose based packaging which includes a paperboard layer or the like that is combined with one or more polymer layers or one or more polymer layers with one or more cellulose based layers. In addition, any of the aforementioned may include a metallic layer that is coated on or between layers using well-known techniques.

The materials appropriate for the present invention can trap odors when the material is processed by the laser system. Treatment of the laser processed material by the methods described herein can remove the odor.

Methods for processing materials resulting in a product wherein the odor has been substantially reduced or eliminated are illustrated in FIGS. 1A and 1B. A first method as illustrated in FIG. 1A includes step 110 of processing a material using a laser system. A variety of methods can be used to convert the material described herein and can be dependent on the specific end use of the package. The laser system is generally used to process the material into sizes that can be assembled together to form a desirable type and size of package.

Methods to reduce the post-laser processing odor include step 120 of heating the material processed in step 110. Without being bound by any theory, it is believed that heating liberates and or vaporizes or decomposes the residual odor causing components produced by laser processing that can be trapped in the material. Heating of the processed material in step 120 can be accomplished using a number of different techniques. Heating can be accomplished via radiation, conduction currents, convection currents and/or chemical applications. Various gases can be utilized to apply the heat as well. Heat treatment can be performed using heat guns, heat plates, heated rollers, heated roller laminator, heat lamps, ovens, microwave ovens and the like. Heat treatment can also be performed using lasers. Heat lamps and/or lasers sources themselves are also capable of supplying the heat to the material. Other methods of supplying heat are also within the scope of this invention. Heating can involve the cycling of low to high temperatures and/or high to low temperatures.

In alternative embodiments, step 110 and step 120 can be conducted simultaneously as opposed to sequentially. In other words, the laser-processed materials can be treated with heat during laser processing as opposed to after laser processing.

The temperature that the material is exposed to during the heat treatment can vary. The temperature may be dependent on the exact material that is used and the length of the exposure to the heat. It is most important that the material be elevated to an optimum temperature for most effective odor reduction. Generally, the material is exposed to temperatures below the scorching temperature of the material. The temperature can be, for example, between about 200° F. and about 500° F. For some materials, temperatures above 500° F. may result in scorching of the material. In some preferred embodiments, the temperature of the surface to be treated is between about 300° F. and about 400° F. Temperatures outside this range are also within the scope of the invention.

The duration of the exposure to heat can vary based on the material, the heat source, the heating temperature and the like. In some exemplary embodiments, the laser processed materials are exposed to heat between about 5 seconds and 20 seconds to sufficiently raise the temperature of the material for optimum odor reduction. With the appropriate heat delivery method the exposure duration can be kept to a minimum.

As further illustrated in FIG. 1B, the methods for reduction of odor may include step 130 of cooling the materials, preferably after the heating step 120. Cooling in step 130 can be accomplished using a variety of techniques including the use of fans, air knifes, cooling plates and the like. Cooling can generally be for short periods of time sufficient to reduce the temperature of the material to allow additional heating cycles if deemed beneficial. Cooling may occur between heating steps as heat dissapates into ambient from the material. The material can be cooled, for example, for at least 3 seconds, preferably at least 5 seconds. In some exemplary embodiments, the heated material is cooled between about 5 seconds and about 60 seconds. The cooling may be directed to only one surface. Alternatively, the cooling may be directed to both surfaces.

The methods for reduction of odor can optionally include additional steps 120b, 130b, 120c and 130c. Steps 120b and 130b represent a second cycle of heating and cooling. Steps 120c and 130c represent a third cycle of heating and cooling. In some embodiments, the materials are exposed to multiple heating and cooling cycles. In some other embodiments, the laser processed materials is exposed to at least 2-3 cycles of heating and cooling are performed to reduce or eliminate the odor. More than 3 cycles of heating and cooling may also be performed and are all within the scope of this invention.

The methods described herein can substantially reduce or eliminate the odor of materials that have been processed using a laser system. Testing of reduction of odor is a subjective test as presently there is no odor detecting equipment. The odor can be evaluated by subjectively sniffing the material and comparing it to a reference sample. Preferably, at least about 85 percent of the odor is eliminated and, more preferably at least about 95 percent of the odor is eliminated by the methods described herein. In some exemplary embodiments, about 95 percent to about 99 percent of the odor is eliminated.

An apparatus for processing the porous materials is illustrated in FIG. 2 at 200 and includes units for converting, heating and cooling systems illustrated as separate units for ease of explanation but in practice may be integrated together. Apparatus 200 includes laser system 230 for converting and heating system 240a for heating the laser treated materials. The apparatus may also include cooling system 250a. Material 210 is placed on conveyor 220 in a manner that laser system 230 can process material 210. After processing by laser system 230, material 210 is heated by heating system 240a and then cooled by cooling system 250a. FIG. 2 also includes a second heating system 240b and a second cooling system 250b. Material 210 can be treated further by another heating/cooling cycle by heating system 240b and cooling system 250b. Heating system 240a and 240b may apply heat to one surface of the material. Alternatively, heating system 240a and 240b may be configured to apply heat to more than one surface of the material. Cooling system 250a and 250b may direct cooling to one surface of the material. Alternatively, cooling system 250a and 250b may be configured to direct cooling to more than one surface of the material. FIG. 2 illustrates an embodiment having two heating systems and two cooling systems to treat the materials to two cycles of heating/cooling. In some embodiments, additional heating and cooling systems may also be employed. In other embodiments, only one heating system (or one heating and cooling system) may be employed.

Alternatively, an apparatus may include only one heating system (or one heating and cooling system) but the material may by treated to multiple cycles of heating and cooling by the same heating and cooling system. The processed material is transported back and forth between heating system and the cooling system for the desired number of cycles.

FIG. 3 illustrates another embodiment of an apparatus for processing materials. Apparatus 300 includes converting, heating and cooling systems as one unit. Apparatus 300 includes laser system 330, heating system 340a and 340b and cooling system 350a and 350b. All of these systems are operably connected by controller 360. Controller 360 can be programmed to operate laser system 330, heating system 340a and 340b and cooling system 350a and 350b in a desired manner as material 310 is conveyed on conveyor 320. Apparatus 300 is shown with two heating and cooling systems. Apparatus with one heating system and one cooling system as well as apparatus with more than two heating and cooling system are also within the scope of this invention.

The reason why heating the laser processed material reduces or eliminates odor is not understood and whatever mechanisms or theories may be implied by this disclosure, the patentability of this invention should not be held to any such one theory. Factors considered to be at work include; diffusivity (odor particles lodged in the material), vaporization (including odor particles trapped in condensated material), increased oxidation at elevated temperatures (increased effectiveness of oxygen in the air at breaking down the odor causing byproducts) and the like.

The present invention is more particularly described in the following example which is intended as an illustration only since numerous modifications and variations within the scope of this invention will be apparent to those skilled in the art.

Example

Converting Using a Laser System

Paperboard was converted for use in packaging. A Preco Flexpro laser system was utilized to convert test samples utilized for odor reduction experiments. It is comprised of a CO₂ laser and various optical components, including a multi axis steered beam galvanometer.

The test pattern for converting comprised of an array of 43 1.461″ long lines spaced 0.04″ apart. This was centered about a 4 in sample coupon of material. The multi-axis steered beam system was used to deliver the laser beam. It was set at 100 in/sec and the laser power was set to cut through nearly 98% of the paper fibers (˜150 watts). As no odor detecting equipment was available the odor was evaluated via subjectively sniffing the material and comparing it to reference samples.

Heating Method 1

The laser converted sample was heated with a heat gun then cooled with shop air. The cycle was repeated 2 times. The heating involved exposing each flat surface of the sample to heat for a few seconds until hot. Cooling was accomplished by blowing shop air across the top and bottom surfaces of the sample for a few seconds each. The output temperature of the heat gun was measured at about 500° F. The opposite surface of the heat-treated sample reached between about 310° F. and 360° F.

Heating Method 2

Alternately, the laser converted sample was heated with a hot plate to elevate the temperature followed by cooling between two room temperature “cooling” plates. Again each surface was heated separately for a few seconds followed by the cooling for a few seconds. A single heating cycle as well as multiple heating/cooling cycles, were performed to see the benefits of odor reduction. As the odor reduction is subjectively evaluated it is difficult to determine the benefit of the 2^nd cycle. One heating cycle optimally applied appeared to be sufficient to provide the desired odor reduction in this method as well as the others. Exposure to about 400° F. for about 10 seconds allowed for significant odor reduction without scorching of the material.

Heating method 3

A heated roller laminator was used to apply the heat to the laser processed samples. A Royal Sovereign RSH-380 unit was set at 302° F. setting (warmed up) and run at a speed setting of 4 or 9. Multiple passes were employed to increase effectiveness—1 pass front side one pass back side, repeated for 3 cycles. Some tests also included air cooling between passes. Wrapping the sample about the top roller (for ˜30 deg wrap angle) was beneficial as it exposes more of the material to the elevated temperature for an increased time.

All of the methods described above resulted in elimination of at least about 95 percent of the odor compared to the material that was not treated with heat.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. A method of reducing odors from a material, the odor caused by laser processing, the method comprising heating the material to a temperature sufficient to substantially reduce the odor.

2. The method of claim 1 wherein the material is a cellulosic, fibrous or paper based material.

3. The method of claim 1 wherein the material is treated to more than one cycle of heating and cooling.

4. The method of claim 1 wherein the heating comprises the use of heat gun, hot plate, heated roller, laser, oven, heat lamp, heated gas, microwaves or combinations thereof.

5. The method of claim 1 wherein the material is heated above 210° F.

6. The method of claim 1 wherein the material is heated to between about 210° F. and about 500° F.

7. The method of claim 1 wherein the material is heated to below a scorching temperature of the material.

8. The method of claim 1 wherein the odor is reduced by at least 90% compared to non heat treated material.

9. The method of claim 1 wherein the heating is performed after processing by the laser converting system.

10. The method of claim 1 wherein the heating is performed concurrently with the laser processing.

11. An article comprising material processed using a laser wherein an odor generated by the laser processing is substantially reduced or eliminated with heat treatment.

12. The article of claim 11 wherein the article is made from cellulosic material, fibrous material or is a paper based product.

13. The article of claim 11 wherein the article has not been subjected to any odor masking agent.

14. The article of claim 11 wherein the odor is reduced by at least 90% compared to an article subjected to laser processing without heat treatment.

15. An apparatus for laser processing an article made from a material, the apparatus comprising:

a laser system for processing the material by burning the material; and

a heating system for heating the material during or after the burning to reduce odor caused by the burning.

16. The apparatus of claim 15 further comprising additional heating and/or cooling system.

17. The apparatus of claim 15 wherein the heating system comprises a heat gun, hot plate, heated roller, laser, oven, heat lamp, microwave or combination thereof

18. The apparatus of claim 16 wherein the cooling system comprises fan, air knife, cold roll, cooling plate, or combination thereof

19. The apparatus of claim 16 wherein the laser system, heating system and cooling system are operably connected by a controller.

20. The apparatus of claim 15 wherein the laser system and the heating system process and heat treat the material simultaneously.